XenServer Documentation

This document is a system administrator's guide to XenServer™, the platform virtualization solution from Citrix®. It describes the tasks involved in configuring a XenServer deployment -- in particular, how to set up storage, networking and resource pools, and how to administer XenServer hosts using the xe command line interface (CLI).

This section summarizes the rest of the guide so that you can find the information you need. The following topics are covered:

XenServer hosts and resource pools
XenServer storage configuration
XenServer network configuration
XenServer workload balancing
XenServer backup and recovery
Monitoring and managing XenServer
XenServer command line interface
XenServer troubleshooting
XenServer resource allocation guidelines

1.1. How this Guide relates to other documentation

This document is primarily aimed at system administrators, who need to configure and administer XenServer deployments. Other documentation shipped with this release includes:

XenServer Installation Guide provides a high level overview of XenServer, along with step-by-step instructions on installing XenServer hosts and the XenCenter management console.
XenServer Virtual Machine Installation Guide describes how to install Linux and Windows VMs on top of a XenServer deployment. As well as installing new VMs from install media (or using the VM templates provided with the XenServer release), this guide also explains how to create VMs from existing physical machines, using a process called P2V.
XenServer Software Development Kit Guide presents an overview of the XenServer SDK -- a selection of code samples that demonstrate how to write applications that interface with XenServer hosts.
XenAPI Specification provides a programmer's reference guide to the XenServer API.
XenServer User Security considers the issues involved in keeping your XenServer installation secure.
Release Notes provides a list of known issues that affect this release.

Chapter 2. XenServer hosts and resource pools

This chapter describes how resource pools can be created through a series of examples using the xe command line interface (CLI). A simple NFS-based shared storage configuration is presented and a number of simple VM management examples are discussed. Procedures for dealing with physical node failures are also described.

2.1. Hosts and resource pools overview

A resource pool comprises multiple XenServer host installations, bound together into a single managed entity which can host Virtual Machines. When combined with shared storage, a resource pool enables VMs to be started on any XenServer host which has sufficient memory and then dynamically moved between XenServer hosts while running with minimal downtime (XenMotion). If an individual XenServer host suffers a hardware failure, then the administrator can restart the failed VMs on another XenServer host in the same resource pool. If high availability (HA) is enabled on the resource pool, VMs will automatically be moved if their host fails. Up to 16 hosts are supported per resource pool, although this restriction is not enforced.

A pool always has at least one physical node, known as the master. Only the master node exposes an administration interface (used by XenCenter and the CLI); the master forwards commands to individual members as necessary.

2.2. Requirements for creating resource pools

A resource pool is an aggregate of one or more homogeneous XenServer hosts, up to a maximum of 16. The definition of homogeneous is:

the CPUs on the server joining the pool are the same (in terms of vendor, model, and features) as the CPUs on servers already in the pool.
the server joining the pool is running the same version of XenServer software, at the same patch level, as servers already in the pool.

The software will enforce additional constraints when joining a server to a pool – in particular:

it is not a member of an existing resource pool
it has no shared storage configured
there are no running or suspended VMs on the XenServer host which is joining
there are no active operations on the VMs in progress, such as one shutting down

You must also check that the clock of the host joining the pool is synchronized to the same time as the pool master (for example, by using NTP), that its management interface is not bonded (you can configure this once the host has successfully joined the pool), and that its management IP address is static (either configured on the host itself or by using an appropriate configuration on your DHCP server).

XenServer hosts in resource pools may contain different numbers of physical network interfaces and have local storage repositories of varying size. In practice, it is often difficult to obtain multiple servers with the exact same CPUs, and so minor variations are permitted. If you are sure that it is acceptable in your environment for hosts with varying CPUs to be part of the same resource pool, then the pool joining operation can be forced by passing a --force parameter.

Note

The requirement for a XenServer host to have a static IP address to be part of a resource pool also applies to servers providing shared NFS or iSCSI storage for the pool.

Although not a strict technical requirement for creating a resource pool, the advantages of pools (for example, the ability to dynamically choose on which XenServer host to run a VM and to dynamically move a VM between XenServer hosts) are only available if the pool has one or more shared storage repositories. If possible, postpone creating a pool of XenServer hosts until shared storage is available. Once shared storage has been added, Citrix recommends that you move existing VMs whose disks are in local storage into shared storage. This can be done using the xe vm-copy command or XenCenter.

2.3. Creating a resource pool

Resource pools can be created using either the XenCenter management console or the CLI. When you join a new host to a resource pool, the joining host synchronizes its local database with the pool-wide one, and inherits some settings from the pool:

VM, local, and remote storage configuration is added to the pool-wide database. All of these will still be tied to the joining host in the pool unless you explicitly take action to make the resources shared after the join has completed.
The joining host inherits existing shared storage repositories in the pool and appropriate PBD records are created so that the new host can access existing shared storage automatically.
Networking information is partially inherited to the joining host: the structural details of NICs, VLANs and bonded interfaces are all inherited, but policy information is not. This policy information, which must be re-configured, includes:
- the location of the management interface, which remains the same as the original configuration. For example, if the other pool hosts have their management interface on a bonded interface, then the joining host must be explicitly migrated to the bond once it has joined. See To add NIC bonds to the pool master and other hosts for details on how to migrate the management interface to a bond.
- Dedicated storage NICs, which must be re-assigned to the joining host from XenCenter or the CLI, and the PBDs re-plugged to route the traffic accordingly. This is because IP addresses are not assigned as part of the pool join operation, and the storage NIC is not useful without this configured correctly. See Section 4.2.6, “Configuring a dedicated storage NIC” for details on how to dedicate a storage NIC from the CLI.

To join XenServer hosts host1 and host2 into a resource pool using the CLI

Open a console on XenServer host host2.
Command XenServer host host2 to join the pool on XenServer host host1 by issuing the command:
```
xe pool-join master-address=<host1> master-username=<root> \
master-password=<password>
```
The master-address must be set to the fully-qualified domain name of XenServer host host1 and the password must be the administrator password set when XenServer host host1 was installed.

Naming a resource pool

XenServer hosts belong to an unnamed pool by default. To create your first resource pool, rename the existing nameless pool. You can use tab-complete to get the <pool_uuid>:
```
xe pool-param-set name-label=<"New Pool"> uuid=<pool_uuid>
```

2.4. Adding shared storage

For a complete list of supported shared storage types, see the Storage chapter. This section demonstrates how shared storage (represented as a storage repository) can be created on an existing NFS server.

Adding NFS shared storage to a resource pool using the CLI

Open a console on any XenServer host in the pool.

Create the storage repository on <server:/path> by issuing the command

xe sr-create content-type=user type=nfs name-label=<"Example SR"> shared=true \
  device-config:server=<server> \
  device-config:serverpath=<path>

The device-config:server refers to the hostname of the NFS server and device-config:serverpath refers to the path on the NFS server. Since shared is set to true, the shared storage will be automatically connected to every XenServer host in the pool and any XenServer hosts that subsequently join will also be connected to the storage. The UUID of the created storage repository will be printed on the screen.

Find the UUID of the pool by the command

xe pool-list

Set the shared storage as the pool-wide default with the command
```
xe pool-param-set uuid=<pool-uuid> default-SR=<sr-uuid>
```
Since the shared storage has been set as the pool-wide default, all future VMs will have their disks created on shared storage by default. See
Chapter 3, Storage for information about creating other types of shared storage.

2.5. Installing and managing VMs on shared storage

The following example shows how to install a Debian Linux VM using the Debian Etch 4.0 template provided with XenServer.

Installing a Debian Etch (4.0) VM

Open a console on any host in the pool.
Use the sr-list command to find the UUID of your shared storage:
```
xe sr-list
```
Create the Debian VM by issuing the command
```
xe vm-install template="Debian Etch 4.0" new-name-label=<etch> \
sr_uuid=<shared_storage_uuid>
```
When the command completes, the Debian VM will be ready to start.
Start the Debian VM with the command
```
xe vm-start vm=<etch>
```
The master will choose a XenServer host from the pool to start the VM. If the on parameter is provided, the VM will start on the specified XenServer host. If the requested XenServer host is unable to start the VM, the command will fail. To request that a VM is always started on a particular XenServer host, set the affinity parameter of the VM to the UUID of the desired XenServer host using the xe vm-param-set command. Once set, the system will start the VM there if it can; if it cannot, it will default to choosing from the set of possible XenServer hosts.
You can use XenMotion to move the Debian VM to another XenServer host with the command
```
xe vm-migrate vm=<etch> host=<host_name> --live
```
XenMotion keeps the VM running during this process to minimize downtime.
Note
When a VM is migrated, the domain on the original hosting server is destroyed and the memory that VM used is zeroed out before Xen makes it available to new VMs. This ensures that there is no information leak from old VMs to new ones. As a consequence, it is possible that sending multiple near-simultaneous commands to migrate a number of VMs, when near the memory limit of a server (for example, a set of VMs consuming 3GB migrated to a server with 4GB of physical memory), the memory of an old domain might not be scrubbed before a migration is attempted, causing the migration to fail with a HOST_NOT_ENOUGH_FREE_MEMORY error. Inserting a delay between migrations should allow Xen the opportunity to successfully scrub the memory and return it to general use.

2.6. Removing a XenServer host from a resource pool

When a XenServer host is removed (ejected) from a pool, the machine is rebooted, reinitialized, and left in a state equivalent to that after a fresh installation. It is important not to eject a XenServer host from a pool if there is important data on the local disks.

To remove a host from a resource pool using the CLI

Open a console on any host in the pool.
Find the UUID of the host b using the command
```
xe host-list
```
Eject the host from the pool:
```
xe pool-eject host-uuid=<uuid>
```
The XenServer host will be ejected and left in a freshly-installed state.

Warning

Do not eject a host from a resource pool if it contains important data stored on its local disks. All of the data will be erased upon ejection from the pool. If you wish to preserve this data, copy the VM to shared storage on the pool first using XenCenter, or the xe vm-copy CLI command.

When a XenServer host containing locally stored VMs is ejected from a pool, those VMs will still be present in the pool database and visible to the other XenServer hosts. They will not start until the virtual disks associated with them have been changed to point at shared storage which can be seen by other XenServer hosts in the pool, or simply removed. It is for this reason that you are strongly advised to move any local storage to shared storage upon joining a pool, so that individual XenServer hosts can be ejected (or physically fail) without loss of data.

2.7. High Availability

This section explains the XenServer implementation of virtual machine high availability (HA), and how to configure it using the xe CLI.

2.8. Enabling HA on a XenServer pool

HA can be enabled on a pool using either XenCenter or the command-line interface. In either case, you will specify a set of priorities that determine which VMs should be given highest restart priority when a pool is overcommitted.

Warning

When HA is enabled, some operations that would compromise the plan for restarting VMs may be disabled, such as removing a server from a pool. To perform these operations, HA can be temporarily disabled, or alternately, VMs protected by HA made unprotected.

2.8.1. Enabling HA using the CLI

Verify that you have a compatible Storage Repository (SR) attached to your pool. iSCSI or Fibre Channel are compatible SR types. Please refer to the reference guide for details on how to configure such a storage repository using the CLI.
For each VM you wish to protect, set a restart priority. You can do this as follows:
```
xe vm-param-set uuid=<vm_uuid> ha-restart-priority=<1> ha-always-run=true
```

Enable HA on the pool:

xe pool-ha-enable heartbeat-sr-uuid=<sr_uuid>

Run the pool-ha-compute-max-host-failures-to-tolerate command. This command returns the maximum number of hosts that can fail before there are insufficient resources to run all the protected VMs in the pool.
```
xe pool-ha-compute-max-host-failures-to-tolerate
```
The number of failures to tolerate determines when an alert is sent: the system will recompute a failover plan as the state of the pool changes and with this computation the system identifies the capacity of the pool and how many more failures are possible without loss of the liveness guarantee for protected VMs. A system alert is generated when this computed value falls below the specified value for ha-host-failures-to-tolerate.
Specify the number of failures to tolerate parameter. This should be less than or equal to the computed value:
```
xe pool-param-set ha-host-failures-to-tolerate=<2>
```

2.8.2. Removing HA protection from a VM using the CLI

To disable HA features for a VM, use the xe vm-param-set command to set the ha-always-run parameter to false. This does not clear the VM restart priority settings. You can enable HA for a VM again by setting the ha-always-run parameter to true.

2.8.3. Recovering an unreachable host

If for some reason a host cannot access the HA statefile, it is possible that a host may become unreachable. To recover your XenServer installation it may be necessary to disable HA using the host-emergency-ha-disable command:

xe host-emergency-ha-disable --force

If the host was the pool master, then it should start up as normal with HA disabled. Slaves should reconnect and automatically disable HA. If the host was a Pool slave and cannot contact the master, then it may be necessary to force the host to reboot as a pool master (xe pool-emergency-transition-to-master) or to tell it where the new master is (xe pool-emergency-reset-master):

xe pool-emergency-transition-to-master uuid=<host_uuid>		
xe pool-emergency-reset-master master-address=<new_master_hostname>

When all hosts have successfully restarted, re-enable HA:

xe pool-ha-enable heartbeat-sr-uuid=<sr_uuid>

2.8.4. Shutting down a host when HA is enabled

When HA is enabled special care needs to be taken when shutting down or rebooting a host to prevent the HA mechanism from assuming that the host has failed. To shutdown a host cleanly in an HA-enabled environment, first disable the host, then evacuate the host and finally shutdown the host using either XenCenter or the CLI. To shutdown a host in an HA-enabled environment on the command line:

xe host-disable host=<host_name>
xe host-evacuate uuid=<host_uuid>
xe host-shutdown host=<host_name>

2.8.5. Shutting down a VM when it is protected by HA

When a VM is protected under a HA plan and set to restart automatically, it cannot be shut down while this protection is active. To shut down a VM, first disable its HA protection and then execute the CLI command. XenCenter offers you a dialog box to automate disabling the protection if you click on the Shutdown button of a protected VM.

Note

If you shut down a VM from within the guest, and the VM is protected, it is automatically restarted under the HA failure conditions. This helps ensure that operator error (or an errant program that mistakenly shuts down the VM) does not result in a protected VM being left shut down accidentally. If you want to shut this VM down, disable its HA protection first.

2.9. Authenticating users using Active Directory (AD)

XenServer supports the authentication of users through AD. This makes it easier to control access to XenServer hosts. Active Directory users can use the xe CLI (passing appropriate -u and -pw arguments) and also connect to the host using XenCenter. Authentication is done on a per-resource pool basis.

Access is controlled by the use of subjects. A subject in XenServer maps to an entity on your directory server (either a user or a group). When external authentication is enabled, the credentials used to create a session are first checked against the local root credentials (in case your directory server is unavailable) and then against the subject list. To permit access, you must create a subject entry for the person or group you wish to grant access to. This can be done using XenCenter or the xe CLI.

2.9.1. Configuring Active Directory authentication

XenServer supports use of Active Directory servers using Windows 2003 or later.

For external authentication using Active Directory to be successful, it is important that the clocks on your XenServer hosts are synchronized with those on your Active Directory server. When XenServer joins the Active Directory domain, this will be checked and authentication will fail if there is too much skew between the servers.

Note

The servers can be in different time-zones, and it is the UTC time that is compared. To ensure synchronization is correct, you may choose to use the same NTP servers for your XenServer pool and the Active Directory server.

When configuring Active Directory authentication for a XenServer host, the same DNS servers should be used for both the Active Directory server (and have appropriate configuration to allow correct interoperability) and XenServer host (note that in some configurations, the active directory server may provide the DNS itself). This can be achieved either using DHCP to provide the IP address and a list of DNS servers to the XenServer host, or by setting values in the PIF objects or using the installer if a manual static configuration is used.

Citrix recommends enabling DCHP to broadcast host names. In particular, the host names localhost or linux should not be assigned to hosts. Host names must consist solely of no more than 156 alphanumeric characters, and may not be purely numeric.

Enabling external authentication on a pool

External authentication using Active Directory can be configured using either XenCenter or the CLi using the command below.
```
xe pool-enable-external-auth auth-type=AD \
        service-name=<full-qualified-domain> \
        config:user=<username> \
        config:pass=<password>
```
The user specified needs to have Add/remove computer objects or workstations privileges, which is the default for domain administrators.
Note
If you are not using DHCP on the network that Active Directory and your XenServer hosts use you can use these two approaches to setup your DNS:
1. Configure the DNS server to use on your XenServer hosts:
```
xe pif-reconfigure-ip mode=static dns=<dnshost>
```
2. Manually set the management interface to use a PIF that is on the same network as your DNS server:
```
xe host-management-reconfigure pif-uuid=<pif_in_the_dns_subnetwork>
```

Note

External authentication is a per-host property. However, Citrix advises that you enable and disable this on a per-pool basis – in this case XenServer will deal with any failures that occur when enabling authentication on a particular host and perform any roll-back of changes that may be required, ensuring that a consistent configuration is used across the pool. Use the host-param-list command to inspect properties of a host and to determine the status of external authentication by checking the values of the relevant fields.

Disabling external authentication

Use XenCenter to disable Active Directory authentication, or the following xe command:
```
xe pool-disable-external-auth
```

2.9.2. User authentication

To allow a user access to your XenServer host, you must add a subject for that user or a group that they are in. (Transitive group memberships are also checked in the normal way, for example: adding a subject for group A, where group A contains group B and user 1 is a member of group B would permit access to user 1.) If you wish to manage user permissions in Active Directory, you could create a single group that you then add and remove users to/from; alternatively, you can add and remove individual users from XenServer, or a combination of users and groups as your would be appropriate for your authentication requirements. The subject list can be managed from XenCenter or using the CLI as described below.

When authenticating a user, the credentials are first checked against the local root account, allowing you to recover a system whose AD server has failed. If the credentials (i.e. username then password) do not match/authenticate, then an authentication request is made to the AD server – if this is successful the user's information will be retrieved and validated against the local subject list, otherwise access will be denied. Validation against the subject list will succeed if the user or a group in the transitive group membership of the user is in the subject list.

Allowing a user access to XenServer using the CLI

To add an AD subject to XenServer:
```
xe subject-add subject-name=<entity name>
```
The entity name should be the name of the user or group to which you want to grant access. You may optionally include the domain of the entity (e.g. '<xendt\user1>' as opposed to '<user1>') although the behavior will be the same unless disambiguation is required.

Removing access for a user using the CLI

Identify the subject identifier for the subject you wish to revoke access. This would be the user or the group containing the user (removing a group would remove access to all users in that group, providing they are not also specified in the subject list). You can do this using the subject list command:

xe subject-list

You may wish to apply a filter to the list, for example to get the subject identifier for a user named user1 in the testad domain, you could use the following command:

xe subject-list other-config:subject-name='<domain\user>'

Remove the user using the subject-remove command, passing in the subject identifier you learned in the previous step:

xe subject-remove subject-identifier=<subject identifier>

You may wish to terminate any current session this user has already authenticated. See Terminating all authenticated sessions using xe and Terminating individual user sessions using xe for more information about terminating sessions. If you do not terminate sessions the users whose permissions have been revoked may be able to continue to access the system until they log out.

Listing subjects with access

To identify the list of users and groups with permission to access your XenServer host or pool, use the following command:
```
xe subject-list
```

2.9.3. Removing access for a user

Once a user is authenticated, they will have access to the server until they end their session, or another user terminates their session. Removing a user from the subject list, or removing them from a group that is in the subject list, will not automatically revoke any already-authenticated sessions that the user has; this means that they may be able to continue to access the pool using XenCenter or other API sessions that they have already created. In order to terminate these sessions forcefully, XenCenter and the CLI provide facilities to terminate individual sessions, or all currently active sessions. See the XenCenter help for more information on procedures using XenCenter, or below for procedures using the CLI.

Terminating all authenticated sessions using xe

Execute the following CLI command:

xe session-subject-identifier-logout-all

Terminating individual user sessions using xe

Determine the subject identifier whose session you wish to log out. Use either the session-subject-identifier-list or subject-list xe commands to find this (the first shows users who have sessions, the second shows all users but can be filtered, for example, using a command like xe subject-list other-config:subject-name=xendt\\user1 – depending on your shell you may need a double-backslash as shown).
Use the session-subject-logout command, passing the subject identifier you have determined in the previous step as a parameter, for example:
```
xe session-subject-identifier-logout subject-identifier=<subject-id>
```

2.9.4. Leaving an AD domain

Use XenCenter to leave an AD domain. See the XenCenter help for more information. Alternately run the pool-disable-external-auth command, specifying the pool uuid if required.

Note

Leaving the domain will not cause the host objects to be removed from the AD database. See this knowledge base article for more information about this and how to remove the disabled host entries.

Chapter 3. Storage

Table of Contents

3.1. Storage Overview

3.1.1. Storage Repositories (SRs)
3.1.2. Virtual Disk Images (VDIs)
3.1.3. Physical Block Devices (PBDs)
3.1.4. Virtual Block Devices (VBDs)
3.1.5. Summary of Storage objects
3.1.6. Virtual Disk Data Formats

3.2. Storage configuration

3.2.1. Creating Storage Repositories
3.2.2. Upgrading LVM storage from XenServer 5.0 or earlier
3.2.3. LVM performance considerations
3.2.4. Converting between VDI formats
3.2.5. Probing an SR
3.2.6. Storage Multipathing

3.3. Storage Repository Types

3.3.1. Local LVM
3.3.2. Local EXT3 VHD
3.3.3. udev
3.3.4. ISO
3.3.5. EqualLogic
3.3.6. NetApp
3.3.7. Software iSCSI Support
3.3.8. Managing Hardware Host Bus Adapters (HBAs)
3.3.9. LVM over iSCSI
3.3.10. NFS VHD
3.3.11. LVM over hardware HBA
3.3.12. Citrix StorageLink Gateway (CSLG) SRs

3.4. Managing Storage Repositories

3.4.1. Destroying or forgetting a SR
3.4.2. Introducing an SR
3.4.3. Resizing an SR
3.4.4. Converting local Fibre Channel SRs to shared SRs
3.4.5. Moving Virtual Disk Images (VDIs) between SRs
3.4.6. Adjusting the disk IO scheduler

3.5. Virtual disk QoS settings

This chapter discusses the framework for storage abstractions. It describes the way physical storage hardware of various kinds is mapped to VMs, and the software objects used by the XenServer host API to perform storage-related tasks. Detailed sections on each of the supported storage types include procedures for creating storage for VMs using the CLI, with type-specific device configuration options, generating snapshots for backup purposes and some best practices for managing storage in XenServer host environments. Finally, the virtual disk QoS (quality of service) settings are described.

3.1. Storage Overview

This section explains what the XenServer storage objects are and how they are related to each other.

3.1.1. Storage Repositories (SRs)

XenServer defines a container called a storage repository (SR) to describe a particular storage target, in which Virtual Disk Images (VDIs) are stored. A VDI is a disk abstraction which contains the contents of a virtual disk.

The interface to storage hardware allows VDIs to be supported on a large number of SR types. The XenServer SR is very flexible, with built-in support for IDE, SATA, SCSI and SAS drives locally connected, and iSCSI, NFS, SAS and Fibre Channel remotely connected. The SR and VDI abstractions allow advanced storage features such as sparse provisioning, VDI snapshots, and fast cloning to be exposed on storage targets that support them. For storage subsystems that do not inherently support advanced operations directly, a software stack is provided based on Microsoft's Virtual Hard Disk (VHD) specification which implements these features.

Each XenServer host can use multiple SRs and different SR types simultaneously. These SRs can be shared between hosts or dedicated to particular hosts. Shared storage is pooled between multiple hosts within a defined resource pool. A shared SR must be network accessible to each host. All hosts in a single resource pool must have at least one shared SR in common.

SRs are storage targets containing virtual disk images (VDIs). SR commands provide operations for creating, destroying, resizing, cloning, connecting and discovering the individual VDIs that they contain.

A storage repository is a persistent, on-disk data structure. For SR types that use an underlying block device, the process of creating a new SR involves erasing any existing data on the specified storage target. Other storage types such as NFS, Netapp, Equallogic and StorageLink SRs, create a new container on the storage array in parallel to existing SRs.

CLI operations to manage storage repositories are described in Section 8.4.14, “SR commands”.

3.1.2. Virtual Disk Images (VDIs)

Virtual Disk Images are a storage abstraction that is presented to a VM. VDIs are the fundamental unit of virtualized storage in XenServer. Similar to SRs, VDIs are persistent, on-disk objects that exist independently of XenServer hosts. CLI operations to manage VDIs are described in Section 8.4.20, “VDI commands”. The actual on-disk representation of the data differs by the SR type and is managed by a separate storage plugin interface for each SR, called the SM API.

3.1.3. Physical Block Devices (PBDs)

Physical Block Devices represent the interface between a physical server and an attached SR. PBDs are connector objects that allow a given SR to be mapped to a XenServer host. PBDs store the device configuration fields that are used to connect to and interact with a given storage target. For example, NFS device configuration includes the IP address of the NFS server and the associated path that the XenServer host mounts. PBD objects manage the run-time attachment of a given SR to a given XenServer host. CLI operations relating to PBDs are described in Section 8.4.10, “PBD commands”.

3.1.4. Virtual Block Devices (VBDs)

Virtual Block Devices are connector objects (similar to the PBD described above) that allows mappings between VDIs and VMs. In addition to providing a mechanism for attaching (also called plugging) a VDI into a VM, VBDs allow for the fine-tuning of parameters regarding QoS (quality of service), statistics, and the bootability of a given VDI. CLI operations relating to VBDs are described in Section 8.4.19, “VBD commands”.

3.1.5. Summary of Storage objects

The following image is a summary of how the storage objects presented so far are related:

Graphical overview of storage repositories and related objects

3.1.6. Virtual Disk Data Formats

In general, there are three types of mapping of physical storage to a VDI:

File-based VHD on a Filesystem; VM images are stored as thin-provisioned VHD format files on either a local non-shared Filesystem (EXT type SR) or a shared NFS target (NFS type SR)
Logical Volume-based VHD on a LUN; The default XenServer blockdevice-based storage inserts a Logical Volume manager on a disk, either a locally attached device (LVM type SR) or a SAN attached LUN over either Fibre Channel (LVMoHBA type SR), iSCSI (LVMoISCSI type SR) or SAS (LVMoHBA type Sr). VDIs are represented as volumes within the Volume manager and stored in VHD format to allow thin provisioning of reference nodes on snapshot and clone.
LUN per VDI; LUNs are directly mapped to VMs as VDIs by SR types that provide an array-specific plugin (Netapp, Equallogic or StorageLink type SRs). The array storage abstraction therefore matches the VDI storage abstraction for environments that manage storage provisioning at an array level.

3.1.6.1. VHD-based VDIs

VHD files may be chained, allowing two VDIs to share common data. In cases where a VHD-backed VM is cloned, the resulting VMs share the common on-disk data at the time of cloning. Each proceeds to make its own changes in an isolated copy-on-write (CoW) version of the VDI. This feature allows VHD-based VMs to be quickly cloned from templates, facilitating very fast provisioning and deployment of new VMs.

The VHD format used by LVM-based and File-based SR types in XenServer uses sparse provisioning. The image file is automatically extended in 2MB chunks as the VM writes data into the disk. For File-based VHD, this has the considerable benefit that VM image files take up only as much space on the physical storage as required. With LVM-based VHD the underlying logical volume container must be sized to the virtual size of the VDI, however unused space on the underlying CoW instance disk is reclaimed when a snapshot or clone occurs. The difference between the two behaviours can be characterised in the following way:

For LVM-based VHDs, the difference disk nodes within the chain consume only as much data as has been written to disk but the leaf nodes (VDI clones) remain fully inflated to the virtual size of the disk. Snapshot leaf nodes (VDI snapshots) remain deflated when not in use and can be attached Read-only to preserve the deflated allocation. Snapshot nodes that are attached Read-Write will be fully inflated on attach, and deflated on detach.
For file-based VHDs, all nodes consume only as much data as has been written, and the leaf node files grow to accommodate data as it is actively written. If a 100GB VDI is allocated for a new VM and an OS is installed, the VDI file will physically be only the size of the OS data that has been written to the disk, plus some minor metadata overhead.

When cloning VMs based off a single VHD template, each child VM forms a chain where new changes are written to the new VM, and old blocks are directly read from the parent template. If the new VM was converted into a further template and more VMs cloned, then the resulting chain will result in degraded performance. XenServer supports a maximum chain length of 30, but it is generally not recommended that you approach this limit without good reason. If in doubt, you can always "copy" the VM using XenServer or the vm-copy command, which resets the chain length back to 0.

3.1.6.1.1. VHD Chain Coalescing

VHD images support chaining, which is the process whereby information shared between one or more VDIs is not duplicated. This leads to a situation where trees of chained VDIs are created over time as VMs and their associated VDIs get cloned. When one of the VDIs in a chain is deleted, XenServer rationalizes the other VDIs in the chain to remove unnecessary VDIs.

This coalescing process runs asynchronously. The amount of disk space reclaimed and the time taken to perform the process depends on the size of the VDI and the amount of shared data. Only one coalescing process will ever be active for an SR. This process thread runs on the SR master host.

If you have critical VMs running on the master server of the pool and experience occasional slow IO due to this process, you can take steps to mitigate against this:

Migrate the VM to a host other than the SR master
Set the disk IO priority to a higher level, and adjust the scheduler. See Section 3.5, “Virtual disk QoS settings” for more information.

3.1.6.1.2. Space Utilisation

Space utilisation is always reported based on the current allocation of the SR, and may not reflect the amount of virtual disk space allocated. The reporting of space for LVM-based SRs versus File-based SRs will also differ given that File-based VHD supports full thin provisioning, while the underlying volume of an LVM-based VHD will be fully inflated to support potential growth for writeable leaf nodes. Space utilisation reported for the SR will depend on the number of snapshots, and the amount of difference data written to a disk between each snapshot.

LVM-based space utilisation differs depending on whether an LVM SR is upgraded vs created as a new SR in XenServer. Upgraded LVM SRs will retain a base node that is fully inflated to the size of the virtual disk, and any subsequent snapshot or clone operations will provision at least one additional node that is fully inflated. For new SRs, in contrast, the base node will be deflated to only the data allocated in the VHD overlay.

When VHD-based VDIs are deleted, the space is marked for deletion on disk. Actual removal of allocated data may take some time to occur as it is handled by the coalesce process that runs asynchronously and independently for each VHD-based SR.

3.1.6.2. LUN-based VDIs

Mapping a raw LUN as a Virtual Disk image is typically the most high-performance storage method. For administrators that want to leverage existing storage SAN infrastructure such as Netapp, Equallogic or StorageLink accessible arrays, the array snapshot, clone and thin provisioning capabilities can be exploited directly using one of the array specific adapter SR types (Netapp, Equallogic or StorageLink). The virtual machine storage operations are mapped directly onto the array APIs using a LUN per VDI representation. This includes activating the data path on demand such as when a VM is started or migrated to another host.

Managed NetApp LUNs are accessible using the NetApp SR driver type, and are hosted on a Network Appliance device running a version of Ontap 7.0 or greater. LUNs are allocated and mapped dynamically to the host using the XenServer host management framework.

EqualLogic storage is accessible using the EqualLogic SR driver type, and is hosted on an EqualLogic storage array running a firmware version of 4.0 or greater. LUNs are allocated and mapped dynamically to the host using the XenServer host management framework.

For further information on StorageLink supported array systems and the various capabilities in each case, please refer to the StorageLink documentation directly.

3.2. Storage configuration

This section covers creating storage repository types and making them available to a XenServer host. The examples provided pertain to storage configuration using the CLI, which provides the greatest flexibility. See the XenCenter Help for details on using the New Storage Repository wizard.

3.2.1. Creating Storage Repositories

This section explains how to create Storage Repositories (SRs) of different types and make them available to a XenServer host. The examples provided cover creating SRs using the xe CLI. See the XenCenter help for details on using the New Storage Repository wizard to add SRs using XenCenter.

Note

Local SRs of type lvm and ext can only be created using the xe CLI. After creation all SR types can be managed by either XenCenter or the xe CLI.

There are two basic steps involved in creating a new storage repository for use on a XenServer host using the CLI:

Probe the SR type to determine values for any required parameters.
Create the SR to initialize the SR object and associated PBD objects, plug the PBDs, and activate the SR.

These steps differ in detail depending on the type of SR being created. In all examples the sr-create command returns the UUID of the created SR if successful.

SRs can also be destroyed when no longer in use to free up the physical device, or forgotten to detach the SR from one XenServer host and attach it to another. See Section 3.4.1, “Destroying or forgetting a SR” for details.

3.2.2. Upgrading LVM storage from XenServer 5.0 or earlier

See the XenServer Installation Guide for information on upgrading LVM storage to enable the latest features. Local, LVM on iSCSI, and LVM on HBA storage types from older (XenServer 5.0 and before) product versions will need to be upgraded before they will support snapshot and fast clone.

Note

Upgrade is a one-way operation so Citrix recommends only performing the upgrade when you are certain the storage will no longer need to be attached to a pool running an older software version.

3.2.3. LVM performance considerations

The snapshot and fast clone functionality provided in XenServer 5.5 and later for LVM-based SRs comes with an inherent performance overhead. In cases where optimal performance is desired, XenServer supports creation of VDIs in the raw format in addition to the default VHD format. The XenServer snapshot functionality is not supported on raw VDIs.

Note

Non-transportable snapshots using the default Windows VSS provider will work on any type of VDI.

Warning

Do not try to snapshot a VM that has type=raw disks attached. This could result in a partial snapshot being created. In this situation, you can identify the orphan snapshot VDIs by checking the snapshot-of field and then deleting them.

3.2.3.1. VDI types

In general, VHD format VDIs will be created. You can opt to use raw at the time you create the VDI; this can only be done using the xe CLI. After software upgrade from a previous XenServer version, existing data will be preserved as backwards-compatible raw VDIs but these are special-cased so that snapshots can be taken of them once you have allowed this by upgrading the SR. Once the SR has been upgraded and the first snapshot has been taken, you will be accessing the data through a VHD format VDI.

To check if an SR has been upgraded, verify that its sm-config:use_vhd key is true. To check if a VDI was created with type=raw, check its sm-config map. The sr-param-list and vdi-param-list xe commands can be used respectively for this purpose.

3.2.3.2. Creating a raw virtual disk using the xe CLI

Run the following command to create a VDI given the UUID of the SR you want to place the virtual disk in:
```
xe vdi-create sr-uuid=<sr-uuid> type=user virtual-size=<virtual-size> name-label=<VDI name>
```
Attach the new virtual disk to a VM and use your normal disk tools within the VM to partition and format, or otherwise make use of the new disk. You can use the vbd-create command to create a new VBD to map the virtual disk into your VM.

3.2.4. Converting between VDI formats

It is not possible to do a direct conversion between the raw and VHD formats. Instead, you can create a new VDI (either raw, as described above, or VHD if the SR has been upgraded or was created on XenServer 5.5 or later) and then copy data into it from an existing volume. Citrix recommends that you use the xe CLI to ensure that the new VDI has a virtual size at least as big as the VDI you are copying from (by checking its virtual-size field, for example by using the vdi-param-list command). You can then attach this new VDI to a VM and use your preferred tool within the VM (standard disk management tools in Windows, or the dd command in Linux) to do a direct block-copy of the data. If the new volume is a VHD volume, it is important to use a tool that can avoid writing empty sectors to the disk so that space is used optimally in the underlying storage repository — in this case a file-based copy approach may be more suitable.

3.2.5. Probing an SR

The sr-probe command can be used in two ways:

To identify unknown parameters for use in creating a SR.
To return a list of existing SRs.

In both cases sr-probe works by specifying an SR type and one or more device-config parameters for that SR type. When an incomplete set of parameters is supplied the sr-probe command returns an error message indicating parameters are missing and the possible options for the missing parameters. When a complete set of parameters is supplied a list of existing SRs is returned. All sr-probe output is returned as XML.

For example, a known iSCSI target can be probed by specifying its name or IP address, and the set of IQNs available on the target will be returned:

xe sr-probe type=lvmoiscsi device-config:target=<192.168.1.10>

Error code: SR_BACKEND_FAILURE_96
Error parameters: , The request is missing or has an incorrect target IQN parameter, \
<?xml version="1.0" ?>
<iscsi-target-iqns>
    <TGT>
        <Index>
            0
        </Index>
        <IPAddress>
            192.168.1.10
        </IPAddress>
        <TargetIQN>
            iqn.192.168.1.10:filer1
        </TargetIQN>
    </TGT>
</iscsi-target-iqns>

Probing the same target again and specifying both the name/IP address and desired IQN returns the set of SCSIids (LUNs) available on the target/IQN.

xe sr-probe type=lvmoiscsi device-config:target=192.168.1.10  \ 
device-config:targetIQN=iqn.192.168.1.10:filer1

Error code: SR_BACKEND_FAILURE_107
Error parameters: , The SCSIid parameter is missing or incorrect, \
<?xml version="1.0" ?>
<iscsi-target>
    <LUN>
        <vendor>
			IET
        </vendor>
        <LUNid>
            0
        </LUNid>
        <size>
            42949672960
        </size>
        <SCSIid>
            149455400000000000000000002000000b70200000f000000
        </SCSIid>
    </LUN>
</iscsi-target>

Probing the same target and supplying all three parameters will return a list of SRs that exist on the LUN, if any.

xe sr-probe type=lvmoiscsi device-config:target=192.168.1.10  \ 
device-config:targetIQN=192.168.1.10:filer1 \
device-config:SCSIid=149455400000000000000000002000000b70200000f000000

<?xml version="1.0" ?>
<SRlist>
    <SR>
        <UUID>
            3f6e1ebd-8687-0315-f9d3-b02ab3adc4a6
        </UUID>
        <Devlist>
            /dev/disk/by-id/scsi-149455400000000000000000002000000b70200000f000000
        </Devlist>
    </SR>
</SRlist>

The following parameters can be probed for each SR type:

SR type	device-config parameter, in order of dependency	Can be probed?	Required for sr-create?
lvmoiscsi	target	No	Yes
	chapuser	No	No
	chappassword	No	No
	targetIQN	Yes	Yes
	SCSIid	Yes	Yes
lvmohba	SCSIid	Yes	Yes
netapp	target	No	Yes
	username	No	Yes
	password	No	Yes
	chapuser	No	No
	chappassword	No	No
	aggregate	No^[a]	Yes
	FlexVols	No	No
	allocation	No	No
	asis	No	No
nfs	server	No	Yes
	serverpath	Yes	Yes
lvm	device	No	Yes
ext	device	No	Yes
equallogic	target	No	Yes
	username	No	Yes
	password	No	Yes
	chapuser	No	No
	chappassword	No	No
	storagepool	No^[b]	Yes
cslg	target	No	Yes
	storageSystemId	Yes	Yes
	storagePoolId	Yes	Yes
	username	No	No ^[c]
	password	No	No ^[c]
	cslport	No	No ^[c]
	chapuser	No	No ^[c]
	chappassword	No	No ^[c]
	provision-type	Yes	No
	protocol	Yes	No
	provision-options	Yes	No
	raid-type	Yes	No
^[a]Aggregate probing is only possible at sr-create time. It needs to be done there so that the aggregate can be specified at the point that the SR is created. ^[b]Storage pool probing is only possible at sr-create time. It needs to be done there so that the aggregate can be specified at the point that the SR is created. ^[c]If the username, password, or port configuration of the StorageLink service are changed from the default value then the appropriate parameter and value must be specified.

3.2.6. Storage Multipathing

Dynamic multipathing support is available for Fibre Channel and iSCSI storage backends. By default, it uses round-robin mode load balancing, so both routes have active traffic on them during normal operation. You can enable multipathing in XenCenter or on the xe CLI.

Caution

Before attempting to enable multipathing, verify that multiple targets are available on your storage server. For example, an iSCSI storage backend queried for sendtargets on a given portal should return multiple targets, as in the following example:

iscsiadm -m discovery --type sendtargets --portal 192.168.0.161
192.168.0.161:3260,1 iqn.strawberry:litchie
192.168.0.204:3260,2 iqn.strawberry:litchie

To enable storage multipathing using the xe CLI

Unplug all PBDs on the host:
```
xe pbd-unplug uuid=<pbd_uuid>
```

Set the host's other-config:multipathing parameter:

xe host-param-set other-config:multipathing=true uuid=host_uuid

Set the host's other-config:multipathhandle parameter to dmp:

xe host-param-set other-config:multipathhandle=dmp uuid=host_uuid

If there are existing SRs on the host running in single path mode but that have multiple paths:
- Migrate or suspend any running guests with virtual disks in affected the SRs
- Unplug and re-plug the PBD of any affected SRs to reconnect them using multipathing:
```
xe pbd-plug uuid=<pbd_uuid>
```

To disable multipathing, first unplug your VBDs, set the host other-config:multipathing parameter to false and then replug your PBDs as described above. Do not modify the other-config:multipathhandle parameter as this will be done automatically.

Multipath support in XenServer is based on the device-mapper multipathd components. Activation and deactivation of multipath nodes is handled automatically by the Storage Manager API. Unlike the standard dm-multipath tools in linux, device mapper nodes are not automatically created for all LUNs on the system, and it is only when LUNs are actively used by the storage management layer that new device mapper nodes are provisioned. It is unnecessary therefore to use any of the dm-multipath CLI tools to query or refresh DM table nodes in XenServer. Should it be necessary to query the status of device-mapper tables manually, or list active device mapper multipath nodes on the system, use the mpathutil utility:

mpathutil list
mpathutil status

Unlike the standard dm-multipath tools in Linux, device mapper nodes are not automatically created for all LUNs on the system. As LUNs are actively used by the storage management layer, new device mapper nodes are provisioned. It is unnecessary to use any of the dm-multipath CLI tools to query or refresh DM table nodes in XenServer.

Note

Due to incompatibilities with the integrated multipath management architecture, the standard dm-multipath CLI utility should not be used with XenServer. Please use the mpathutil CLI tool for querying the status of nodes on the host.

Note

Multipath support in Equallogic arrays does not encompass Storage IO multipathing in the traditional sense of the term. Multipathing must be handled at the network/NIC bond level. Refer to the Equallogic documentation for information about configuring network failover for Equallogic SRs/LVMoISCSI SRs.

3.3. Storage Repository Types

The storage repository types supported in XenServer are provided by plug-ins in the control domain; these can be examined and plugins supported by third parties can be added to the /opt/xensource/sm directory. Modification of these files is unsupported, but visibility of these files may be valuable to developers and power users. New storage manager plugins placed in this directory are automatically detected by XenServer. Use the sm-list command (see Section 8.4.13, “Storage Manager commands”) to list the available SR types .

New storage repositories are created using the New Storage wizard in XenCenter. The wizard guides you through the various probing and configuration steps. Alternatively, use the sr-create command. This command creates a new SR on the storage substrate (potentially destroying any existing data), and creates the SR API object and a corresponding PBD record, enabling VMs to use the storage. On successful creation of the SR, the PBD is automatically plugged. If the SR shared=true flag is set, a PBD record is created and plugged for every XenServer Host in the resource pool.

All XenServer SR types support VDI resize, fast cloning and snapshot. SRs based on the LVM SR type (local, iSCSI, or HBA) provide thin provisioning for snapshot and hidden parent nodes. The other SR types support full thin provisioning, including for virtual disks that are active.

Note

Automatic LVM metadata archiving is disabled by default. This does not prevent metadata recovery for LVM groups.

Warning

When VHD VDIs are not attached, for example in the case of a VDI snapshot, they are stored by default thinly-provisioned. Because of this it is imperative to ensure that there is sufficient disk-space available for the VDI to become thickly provisioned when attempting to attach it. VDI clones, however, are thickly-provisioned.

The maximum supported VDI sizes are:

Storage type	Maximum VDI size
EXT3	2TB
LVM	2TB
Netapp	2TB
EqualLogic	15TB
ONTAP(NetApp)	12TB

3.3.1. Local LVM

The Local LVM type presents disks within a locally-attached Volume Group.

By default, XenServer uses the local disk on the physical host on which it is installed. The Linux Logical Volume Manager (LVM) is used to manage VM storage. A VDI is implemented in VHD format in an LVM logical volume of the specified size.

XenServer versions prior to 5.5.0 did not use the VHD format and will remain in legacy mode. See Section 3.2.2, “Upgrading LVM storage from XenServer 5.0 or earlier” for information about upgrading a storage repository to the new format.

3.3.1.1. Creating a local LVM SR (lvm)

Device-config parameters for lvm SRs are:

Parameter Name	Description	Required?
Device	device name on the local host to use for the SR	Yes

To create a local lvm SR on /dev/sdb use the following command.

xe sr-create host-uuid=<valid_uuid> content-type=user \
name-label=<"Example Local LVM SR"> shared=false \
device-config:device=/dev/sdb type=lvm

3.3.2. Local EXT3 VHD

The Local EXT3 VHD type represents disks as VHD files stored on a local path.

Local disks can also be configured with a local EXT SR to serve VDIs stored in the VHD format. Local disk EXT SRs must be configured using the XenServer CLI.

By definition, local disks are not shared across pools of XenServer host. As a consequence, VMs whose VDIs are stored in SRs on local disks are not agile -- they cannot be migrated between XenServer hosts in a resource pool.

3.3.2.1. Creating a local EXT3 SR (ext)

Device-config parameters for ext SRs:

Parameter Name	Description	Required?
Device	device name on the local host to use for the SR	Yes

To create a local ext SR on /dev/sdb use the following command:

xe sr-create host-uuid=<valid_uuid> content-type=user \
name-label=<"Example Local EXT3 SR"> shared=false \
device-config:device=/dev/sdb type=ext

3.3.3. udev

The udev type represents devices plugged in using the udev device manager as VDIs.

XenServer has two SRs of type udev that represent removable storage. One is for the CD or DVD disk in the physical CD or DVD-ROM drive of the XenServer host. The other is for a USB device plugged into a USB port of the XenServer host. VDIs that represent the media come and go as disks or USB sticks are inserted and removed.

3.3.4. ISO

The ISO type handles CD images stored as files in ISO format. This SR type is useful for creating shared ISO libraries.

3.3.5. EqualLogic

The EqualLogic SR type maps LUNs to VDIs on a EqualLogic array group, allowing for the use of fast snapshot and clone features on the array.

If you have access to an EqualLogic filer, you can configure a custom EqualLogic storage repository for VM storage on you XenServer deployment. This allows the use of the advanced features of this filer type. Virtual disks are stored on the filer using one LUN per virtual disk. Using this storage type will enable the thin provisioning, snapshot, and fast clone features of this filer.

Consider your storage requirements when deciding whether to use the specialized SR plugin, or to use the generic LVM/iSCSI storage backend. By using the specialized plugin, XenServer will communicate with the filer to provision storage. Some arrays have a limitation of seven concurrent connections, which may limit the throughput of control operations. Using the plugin will allow you to make use of the advanced array features, however, so will make backup and snapshot operations easier.

Warning

There are two types of administration accounts that can successfully access the EqualLogic SM plugin:

A group administration account which has access to and can manage the entire group and all storage pools.
A pool administrator account that can manage only the objects (SR and VDI snapshots) that are in the pool or pools assigned to the account.

3.3.5.1. Creating a shared EqualLogic SR

Device-config parameters for EqualLogic SRs:

Parameter Name	Description	Optional?
target	the IP address or hostname of the EqualLogic array that hosts the SR	no
username	the login username used to manage the LUNs on the array	no
password	the login password used to manage the LUNs on the array	no
storagepool	the storage pool name	no
chapuser	the username to be used for CHAP authentication	yes
chappassword	the password to be used for CHAP authentication	yes
allocation	specifies whether to use thick or thin provisioning. Default is thick. Thin provisioning reserves a minimum of 10% of volume space.	yes
snap-reserve-percentage	sets the amount of space, as percentage of volume reserve, to allocate to snapshots. Default is 100%.	yes
snap-depletion	sets the action to take when snapshot reserve space is exceeded. `volume-offline` sets the volume and all its snapshots offline. This is the default action. The `delete-oldest` action deletes the oldest snapshot until enough space is available for creating the new snapshot.	yes

Use the sr-create command to create an EqualLogic SR. For example:

xe sr-create host-uuid=<valid_uuid> content-type=user \
name-label=<"Example shared Equallogic SR"> \
shared=true device-config:target=<target_ip> \
device-config:username=<admin_username> \
device-config:password=<admin_password> \
device-config:storagepool=<my_storagepool> \
device-config:chapuser=<chapusername> \
device-config:chappassword=<chapuserpassword> \
device-config:allocation=<thick> \
type=equal

3.3.6. NetApp

The NetApp type maps LUNs to VDIs on a NetApp server, enabling the use of fast snapshot and clone features on the filer.

Note

NetApp and EqualLogic SRs require a Citrix Essentials for XenServer license. To learn more about Citrix Essentials for XenServer and to find out how to upgrade, visit the Citrix website here.

If you have access to Network Appliance™ (NetApp) storage with sufficient disk space, running a version of Data ONTAP 7G (version 7.0 or greater), you can configure a custom NetApp storage repository for VM storage on your XenServer deployment. The XenServer driver uses the ZAPI interface to the storage to create a group of FlexVols that correspond to an SR. VDIs are created as virtual LUNs on the storage, and attached to XenServer hosts using an iSCSI data path. There is a direct mapping between a VDI and a raw LUN that does not require any additional volume metadata. The NetApp SR is a managed volume and the VDIs are the LUNs within the volume. VM cloning uses the snapshotting and cloning capabilities of the storage for data efficiency and performance and to ensure compatibility with existing ONTAP management tools.

As with the iSCSI-based SR type, the NetApp driver also uses the built-in software initiator and its assigned host IQN, which can be modified by changing the value shown on the General tab when the storage repository is selected in XenCenter.

The easiest way to create NetApp SRs is to use XenCenter. See the XenCenter help for details. See Section 3.3.6.1, “Creating a shared NetApp SR over iSCSI” for an example of how to create them using the xe CLI.

FlexVols

NetApp uses FlexVols as the basic unit of manageable data. There are limitations that constrain the design of NetApp-based SRs. These are:

maximum number of FlexVols per filer
maximum number of LUNs per network port
maximum number of snapshots per FlexVol

Precise system limits vary per filer type, however as a general guide, a FlexVol may contain up to 200 LUNs, and provides up to 255 snapshots. Because there is a one-to-one mapping of LUNs to VDIs, and because often a VM will have more than one VDI, the resource limitations of a single FlexVol can easily be reached. Also, the act of taking a snapshot includes snapshotting all the LUNs within a FlexVol and the VM clone operation indirectly relies on snapshots in the background as well as the VDI snapshot operation for backup purposes.

There are two constraints to consider when mapping the virtual storage objects of the XenServer host to the physical storage. To maintain space efficiency it makes sense to limit the number of LUNs per FlexVol, yet at the other extreme, to avoid resource limitations a single LUN per FlexVol provides the most flexibility. However, because there is a vendor-imposed limit of 200 or 500 FlexVols, per filer (depending on the NetApp model), this creates a limit of 200 or 500 VDIs per filer and it is therefore important to select a suitable number of FlexVols taking these parameters into account.

Given these resource constraints, the mapping of virtual storage objects to the Ontap storage system has been designed in the following manner. LUNs are distributed evenly across FlexVols, with the expectation of using VM UUIDs to opportunistically group LUNs attached to the same VM into the same FlexVol. This is a reasonable usage model that allows a snapshot of all the VDIs in a VM at one time, maximizing the efficiency of the snapshot operation.

An optional parameter you can set is the number of FlexVols assigned to the SR. You can use between 1 and 32 FlexVols; the default is 8. The trade-off in the number of FlexVols to the SR is that, for a greater number of FlexVols, the snapshot and clone operations become more efficient, because there are fewer VMs backed off the same FlexVol. The disadvantage is that more FlexVol resources are used for a single SR, where there is a typical system-wide limitation of 200 for some smaller filers.

Aggregates

When creating a NetApp driver-based SR, you select an appropriate aggregate. The driver can be probed for non-traditional type aggregates, that is, newer-style aggregates that support FlexVols, and lists all aggregates available and the unused disk space on each.

Note

Aggregate probing is only possible at sr-create time so that the aggregate can be specified at the point that the SR is created, but is not probed by the sr-probe command.

Citrix strongly recommends that you configure an aggregate exclusively for use by XenServer storage, because space guarantees and allocation cannot be correctly managed if other applications are sharing the resource.

Thick or thin provisioning

When creating NetApp storage, you can also choose the type of space management used. By default, allocated space is thickly provisioned to ensure that VMs never run out of disk space and that all virtual allocation guarantees are fully enforced on the filer. Selecting thick provisioning ensures that whenever a VDI (LUN) is allocated on the filer, sufficient space is reserved to guarantee that it will never run out of space and consequently experience failed writes to disk. Due to the nature of the Ontap FlexVol space provisioning algorithms the best practice guidelines for the filer require that at least twice the LUN space is reserved to account for background snapshot data collection and to ensure that writes to disk are never blocked. In addition to the double disk space guarantee, Ontap also requires some additional space reservation for management of unique blocks across snapshots. The guideline on this amount is 20% above the reserved space. The space guarantees afforded by thick provisioning will reserve up to 2.4 times the requested virtual disk space.

The alternative allocation strategy is thin provisioning, which allows the administrator to present more storage space to the VMs connecting to the SR than is actually available on the SR. There are no space guarantees, and allocation of a LUN does not claim any data blocks in the FlexVol until the VM writes data. This might be appropriate for development and test environments where you might find it convenient to over-provision virtual disk space on the SR in the anticipation that VMs might be created and destroyed frequently without ever utilizing the full virtual allocated disk.

Warning

If you are using thin provisioning in production environments, take appropriate measures to ensure that you never run out of storage space. VMs attached to storage that is full will fail to write to disk, and in some cases may fail to read from disk, possibly rendering the VM unusable.

FAS Deduplication

FAS Deduplication is a NetApp technology for reclaiming redundant disk space. Newly-stored data objects are divided into small blocks, each block containing a digital signature, which is compared to all other signatures in the data volume. If an exact block match exists, the duplicate block is discarded and the disk space reclaimed. FAS Deduplication can be enabled on thin provisioned NetApp-based SRs and operates according to the default filer FAS Deduplication parameters, typically every 24 hours. It must be enabled at the point the SR is created and any custom FAS Deduplication configuration must be managed directly on the filer.

Access Control

Because FlexVol operations such as volume creation and volume snapshotting require administrator privileges on the filer itself, Citrix recommends that the XenServer host is provided with suitable administrator username and password credentials at configuration time. In situations where the XenServer host does not have full administrator rights to the filer, the filer administrator could perform an out-of-band preparation and provisioning of the filer and then introduce the SR to the XenServer host using XenCenter or the sr-introduce xe CLI command. Note, however, that operations such as VM cloning or snapshot generation will fail in this situation due to insufficient access privileges.

Licenses

You need to have an iSCSI license on the NetApp filer to use this storage repository type; for the generic plugins you need either an iSCSI or NFS license depending on the SR type being used.

Further information

For more information about NetApp technology, see the following links:

3.3.6.1. Creating a shared NetApp SR over iSCSI

Device-config parameters for netapp SRs:

Parameter Name	Description	Optional?
target	the IP address or hostname of the NetApp server that hosts the SR	no
port	the port to use for connecting to the NetApp server that hosts the SR. Default is port 80.	yes
usehttps	specifies whether to use a secure TLS-based connection to the NetApp server that hosts the SR [true\|false]. Default is false.	yes
username	the login username used to manage the LUNs on the filer	no
password	the login password used to manage the LUNs on the filer	no
aggregate	the aggregate name on which the FlexVol is created	Required for sr_create
FlexVols	the number of FlexVols to allocate to each SR	yes
chapuser	the username for CHAP authentication	yes
chappassword	the password for CHAP authentication	yes
allocation	specifies whether to provision LUNs using thick or thin provisioning. Default is thick	yes
asis	specifies whether to use FAS Deduplication if available. Default is false	yes

Setting the SR other-config:multiplier parameter to a valid value adjusts the default multiplier attribute. By default XenServer allocates 2.4 times the requested space to account for snapshot and metadata overhead associated with each LUN. To save disk space, you can set the multiplier to a value >= 1. Setting the multiplier should only be done with extreme care by system administrators who understand the space allocation constraints of the NetApp filer. If you try to set the amount to less then 1, for example, in an attempt to pre-allocate very little space for the LUN, the attempt will most likely fail.

Setting the SR other-config:enforce_allocation parameter to true resizes the FlexVols to precisely the amount specified by either the multiplier value above, or the default 2.4 value.

Note

This works on new VDI creation in the selected FlexVol, or on all FlexVols during an SR scan and overrides any manual size adjustments made by the administrator to the SR FlexVols.

To create a NetApp SR, use the following command.

xe sr-create host-uuid=<valid_uuid> content-type=user \
  name-label=<"Example shared NetApp SR"> shared=true \
  device-config:target=<192.168.1.10> device-config:username=<admin_username> \
  device-config:password=<admin_password> \
  type=netapp

3.3.6.2. Managing VDIs in a NetApp SR

Due to the complex nature of mapping VM storage objects onto NetApp storage objects such as LUNs, FlexVols and disk Aggregates, the plugin driver makes some general assumptions about how storage objects should be organized. The default number of FlexVols that are managed by an SR instance is 8, named XenStorage_<SR_UUID>_FV<#> where # is a value between 0 and the total number of FlexVols assigned. This means that VDIs (LUNs) are evenly distributed across any one of the FlexVols at the point that the VDI is instantiated. The only exception to this rule is for groups of VM disks which are opportunistically assigned to the same FlexVol to assist with VM cloning, and when VDIs are created manually but passed a vmhint flag that informs the backend of the FlexVol to which the VDI should be assigned. The vmhint may be a random string such as a uuid that is re-issued for all subsequent VDI creation operations to ensure grouping in the same FlexVol, or it can be a simple FlexVol number to correspond to the FlexVol naming convention applied on the Filer. Using either of the following 2 commands, a VDI created manually using the CLI can be assigned to a specific FlexVol:

xe vdi-create uuid=<valid_vdi_uuid> sr-uuid=<valid_sr_uuid> \
sm-config:vmhint=<valid_vm_uuid>

xe vdi-create uuid=<valid_vdi_uuid> sr-uuid=<valid_sr_uuid> \
sm-config:vmhint=<valid_flexvol_number>

3.3.6.3. Taking VDI snapshots with a NetApp SR

Cloning a VDI entails generating a snapshot of the FlexVol and then creating a LUN clone backed off the snapshot. When generating a VM snapshot you must snapshot each of the VMs disks in sequence. Because all the disks are expected to be located in the same FlexVol, and the FlexVol snapshot operates on all LUNs in the same FlexVol, it makes sense to re-use an existing snapshot for all subsequent LUN clones. By default, if no snapshot hint is passed into the backend driver it will generate a random ID with which to name the FlexVol snapshot. There is a CLI override for this value, passed in as an epochhint. The first time the epochhint value is received, the backend generates a new snapshot based on the cookie name. Any subsequent snapshot requests with the same epochhint value will be backed off the existing snapshot:

xe vdi-snapshot uuid=<valid_vdi_uuid> driver-params:epochhint=<cookie>

During NetApp SR provisioning, additional disk space is reserved for snapshots. If you plan to not use the snapshotting functionality, you might want to free up this reserved space. To do so, you can reduce the value of the other-config:multiplier parameter. By default the value of the multiplier is 2.4, so the amount of space reserved is 2.4 times the amount of space that would be needed for the FlexVols themselves.

3.3.7. Software iSCSI Support

XenServer provides support for shared SRs on iSCSI LUNs. iSCSI is supported using the open-iSCSI software iSCSI initiator or by using a supported iSCSI Host Bus Adapter (HBA). The steps for using iSCSI HBAs are identical to those for Fibre Channel HBAs, both of which are described in Section 3.3.9.2, “Creating a shared LVM over Fibre Channel / iSCSI HBA or SAS SR (lvmohba)”.

Shared iSCSI support using the software iSCSI initiator is implemented based on the Linux Volume Manager (LVM) and provides the same performance benefits provided by LVM VDIs in the local disk case. Shared iSCSI SRs using the software-based host initiator are capable of supporting VM agility using XenMotion: VMs can be started on any XenServer host in a resource pool and migrated between them with no noticeable downtime.

iSCSI SRs use the entire LUN specified at creation time and may not span more than one LUN. CHAP support is provided for client authentication, during both the data path initialization and the LUN discovery phases.

3.3.7.1. XenServer Host iSCSI configuration

All iSCSI initiators and targets must have a unique name to ensure they can be uniquely identified on the network. An initiator has an iSCSI initiator address, and a target has an iSCSI target address. Collectively these are called iSCSI Qualified Names, or IQNs.

XenServer hosts support a single iSCSI initiator which is automatically created and configured with a random IQN during host installation. The single initiator can be used to connect to multiple iSCSI targets concurrently.

iSCSI targets commonly provide access control using iSCSI initiator IQN lists, so all iSCSI targets/LUNs to be accessed by a XenServer host must be configured to allow access by the host's initiator IQN. Similarly, targets/LUNs to be used as shared iSCSI SRs must be configured to allow access by all host IQNs in the resource pool.

Note

iSCSI targets that do not provide access control will typically default to restricting LUN access to a single initiator to ensure data integrity. If an iSCSI LUN is intended for use as a shared SR across multiple XenServer hosts in a resource pool, ensure that multi-initiator access is enabled for the specified LUN.

The XenServer host IQN value can be adjusted using XenCenter, or using the CLI with the following command when using the iSCSI software initiator:

xe host-param-set uuid=<valid_host_id> other-config:iscsi_iqn=<new_initiator_iqn>

Warning

It is imperative that every iSCSI target and initiator have a unique IQN. If a non-unique IQN identifier is used, data corruption and/or denial of LUN access can occur.

Warning

Do not change the XenServer host IQN with iSCSI SRs attached. Doing so can result in failures connecting to new targets or existing SRs.

3.3.8. Managing Hardware Host Bus Adapters (HBAs)

This section covers various operations required to manage SAS, Fibre Channel and iSCSI HBAs.

3.3.8.1. Sample QLogic iSCSI HBA setup

For full details on configuring QLogic Fibre Channel and iSCSI HBAs please refer to the QLogic website.

Once the HBA is physically installed into the XenServer host, use the following steps to configure the HBA:

Set the IP networking configuration for the HBA. This example assumes DHCP and HBA port 0. Specify the appropriate values if using static IP addressing or a multi-port HBA.
```
/opt/QLogic_Corporation/SANsurferiCLI/iscli -ipdhcp 0
```

Add a persistent iSCSI target to port 0 of the HBA.

/opt/QLogic_Corporation/SANsurferiCLI/iscli -pa 0 <iscsi_target_ip_address>

Use the xe sr-probe command to force a rescan of the HBA controller and display available LUNs. See Section 3.2.5, “Probing an SR” and Section 3.3.9.2, “Creating a shared LVM over Fibre Channel / iSCSI HBA or SAS SR (lvmohba)” for more details.

3.3.8.2. Removing HBA-based SAS, FC or iSCSI device entries

Note

This step is not required. Citrix recommends that only power users perform this process if it is necessary.

Each HBA-based LUN has a corresponding global device path entry under /dev/disk/by-scsibus in the format <SCSIid>-<adapter>:<bus>:<target>:<lun> and a standard device path under /dev. To remove the device entries for LUNs no longer in use as SRs use the following steps:

Use sr-forget or sr-destroy as appropriate to remove the SR from the XenServer host database. See Section 3.4.1, “Destroying or forgetting a SR” for details.
Remove the zoning configuration within the SAN for the desired LUN to the desired host.
Use the sr-probe command to determine the ADAPTER, BUS, TARGET, and LUN values corresponding to the LUN to be removed. See Section 3.2.5, “Probing an SR” for details.

Remove the device entries with the following command:

echo "1" > /sys/class/scsi_device/<adapter>:<bus>:<target>:<lun>/device/delete

Warning

Make absolutely sure you are certain which LUN you are removing. Accidentally removing a LUN required for host operation, such as the boot or root device, will render the host unusable.

3.3.9. LVM over iSCSI

The LVM over iSCSI type represents disks as Logical Volumes within a Volume Group created on an iSCSI LUN.

3.3.9.1. Creating a shared LVM over iSCSI SR using the software iSCSI initiator (lvmoiscsi)

Device-config parameters for lvmoiscsi SRs:

Parameter Name	Description	Optional?
target	the IP address or hostname of the iSCSI filer that hosts the SR	yes
targetIQN	the IQN target address of iSCSI filer that hosts the SR	yes
SCSIid	the SCSI bus ID of the destination LUN	yes
chapuser	the username to be used for CHAP authentication	no
chappassword	the password to be used for CHAP authentication	no
port	the network port number on which to query the target	no
usediscoverynumber	the specific iscsi record index to use	no

To create a shared lvmoiscsi SR on a specific LUN of an iSCSI target use the following command.

xe sr-create host-uuid=<valid_uuid> content-type=user \
name-label=<"Example shared LVM over iSCSI SR"> shared=true \
device-config:target=<target_ip=> device-config:targetIQN=<target_iqn=> \
device-config:SCSIid=<scsci_id> \
type=lvmoiscsi

3.3.9.2. Creating a shared LVM over Fibre Channel / iSCSI HBA or SAS SR (lvmohba)

SRs of type lvmohba can be created and managed using the xe CLI or XenCenter.

Device-config parameters for lvmohba SRs:

Parameter name	Description	Required?
SCSIid	Device SCSI ID	Yes

To create a shared lvmohba SR, perform the following steps on each host in the pool:

Zone in one or more LUNs to each XenServer host in the pool. This process is highly specific to the SAN equipment in use. Please refer to your SAN documentation for details.
If necessary, use the HBA CLI included in the XenServer host to configure the HBA:
- Emulex: /usr/sbin/hbanyware
- QLogic FC: /opt/QLogic_Corporation/SANsurferCLI
- QLogic iSCSI: /opt/QLogic_Corporation/SANsurferiCLI
See
Section 3.3.8, “Managing Hardware Host Bus Adapters (HBAs)” for an example of QLogic iSCSI HBA configuration. For more information on Fibre Channel and iSCSI HBAs please refer to the Emulex and QLogic websites.

Use the sr-probe command to determine the global device path of the HBA LUN. sr-probe forces a re-scan of HBAs installed in the system to detect any new LUNs that have been zoned to the host and returns a list of properties for each LUN found. Specify the host-uuid parameter to ensure the probe occurs on the desired host. The global device path returned as the <path> property will be common across all hosts in the pool and therefore must be used as the value for the device-config:device parameter when creating the SR. If multiple LUNs are present use the vendor, LUN size, LUN serial number, or the SCSI ID as included in the <path> property to identify the desired LUN.

xe sr-probe type=lvmohba \
host-uuid=1212c7b3-f333-4a8d-a6fb-80c5b79b5b31
Error code: SR_BACKEND_FAILURE_90
Error parameters: , The request is missing the device parameter, \
<?xml version="1.0" ?>
<Devlist>
    <BlockDevice>
        <path>
            /dev/disk/by-id/scsi-360a9800068666949673446387665336f
        </path>
        <vendor>
            HITACHI
        </vendor>
        <serial>
            730157980002
        </serial>
        <size>
            80530636800
        </size>
        <adapter>
            4
        </adapter>
        <channel>
            0
        </channel>
        <id>
            4
        </id>
        <lun>
            2
        </lun>
        <hba>
            qla2xxx
        </hba>
    </BlockDevice>
    <Adapter>
        <host>
            Host4
        </host>
        <name>
            qla2xxx
        </name>
        <manufacturer>
            QLogic HBA Driver
        </manufacturer>
        <id>
            4
        </id>
    </Adapter>
</Devlist>

On the master host of the pool create the SR, specifying the global device path returned in the <path> property from sr-probe. PBDs will be created and plugged for each host in the pool automatically.

xe sr-create host-uuid=<valid_uuid> \
content-type=user \
name-label=<"Example shared LVM over HBA SR"> shared=true \
device-config:SCSIid=<device_scsi_id> type=lvmohba

Note

You can use the BRAND_CONSOLE; Repair Storage Repository function to retry the PBD creation and plugging portions of the sr-create operation. This can be valuable in cases where the LUN zoning was incorrect for one or more hosts in a pool when the SR was created. Correct the zoning for the affected hosts and use the Repair Storage Repository function instead of removing and re-creating the SR.

3.3.10. NFS VHD

The NFS VHD type stores disks as VHD files on a remote NFS filesystem.

NFS is a ubiquitous form of storage infrastructure that is available in many environments. XenServer allows existing NFS servers that support NFS V3 over TCP/IP to be used immediately as a storage repository for virtual disks (VDIs). VDIs are stored in the Microsoft VHD format only. Moreover, as NFS SRs can be shared, VDIs stored in a shared SR allow VMs to be started on any XenServer hosts in a resource pool and be migrated between them using XenMotion with no noticeable downtime.

Creating an NFS SR requires the hostname or IP address of the NFS server. The sr-probe command provides a list of valid destination paths exported by the server on which the SR can be created. The NFS server must be configured to export the specified path to all XenServer hosts in the pool, or the creation of the SR and the plugging of the PBD record will fail.

As mentioned at the beginning of this chapter, VDIs stored on NFS are sparse. The image file is allocated as the VM writes data into the disk. This has the considerable benefit that VM image files take up only as much space on the NFS storage as is required. If a 100GB VDI is allocated for a new VM and an OS is installed, the VDI file will only reflect the size of the OS data that has been written to the disk rather than the entire 100GB.

VHD files may also be chained, allowing two VDIs to share common data. In cases where a NFS-based VM is cloned, the resulting VMs will share the common on-disk data at the time of cloning. Each will proceed to make its own changes in an isolated copy-on-write version of the VDI. This feature allows NFS-based VMs to be quickly cloned from templates, facilitating very fast provisioning and deployment of new VMs.

Note

The maximum supported length of VHD chains is 30.

As VHD-based images require extra metadata to support sparseness and chaining, the format is not as high-performance as LVM-based storage. In cases where performance really matters, it is well worth forcibly allocating the sparse regions of an image file. This will improve performance at the cost of consuming additional disk space.

XenServer's NFS and VHD implementations assume that they have full control over the SR directory on the NFS server. Administrators should not modify the contents of the SR directory, as this can risk corrupting the contents of VDIs.

XenServer has been tuned for enterprise-class storage that use non-volatile RAM to provide fast acknowledgments of write requests while maintaining a high degree of data protection from failure. XenServer has been tested extensively against Network Appliance FAS270c and FAS3020c storage, using Data OnTap 7.2.2.

In situations where XenServer is used with lower-end storage, it will cautiously wait for all writes to be acknowledged before passing acknowledgments on to guest VMs. This will incur a noticeable performance cost, and might be remedied by setting the storage to present the SR mount point as an asynchronous mode export. Asynchronous exports acknowledge writes that are not actually on disk, and so administrators should consider the risks of failure carefully in these situations.

The XenServer NFS implementation uses TCP by default. If your situation allows, you can configure the implementation to use UDP in situations where there may be a performance benefit. To do this, specify the device-config parameter useUDP=true at SR creation time.

Warning

Since VDIs on NFS SRs are created as sparse, administrators must ensure that there is enough disk space on the NFS SRs for all required VDIs. XenServer hosts do not enforce that the space required for VDIs on NFS SRs is actually present.

3.3.10.1. Creating a shared NFS SR (nfs)

Device-config parameters for nfs SRs:

Parameter Name	Description	Required?
server	IP address or hostname of the NFS server	Yes
serverpath	path, including the NFS mount point, to the NFS server that hosts the SR	Yes

To create a shared NFS SR on 192.168.1.10:/export1 use the following command.

xe sr-create host-uuid=<host_uuid> content-type=user \
name-label=<"Example shared NFS SR"> shared=true \
device-config:server=<192.168.1.10> device-config:serverpath=</export1> type=nfs

3.3.11. LVM over hardware HBA

The LVM over hardware HBA type represents disks as VHDs on Logical Volumes within a Volume Group created on an HBA LUN providing, for example, hardware-based iSCSI or FC support.

XenServer hosts support Fibre Channel (FC) storage area networks (SANs) through Emulex or QLogic host bus adapters (HBAs). All FC configuration required to expose a FC LUN to the host must be completed manually, including storage devices, network devices, and the HBA within the XenServer host. Once all FC configuration is complete the HBA will expose a SCSI device backed by the FC LUN to the host. The SCSI device can then be used to access the FC LUN as if it were a locally attached SCSI device.

Use the sr-probe command to list the LUN-backed SCSI devices present on the host. This command forces a scan for new LUN-backed SCSI devices. The path value returned by sr-probe for a LUN-backed SCSI device is consistent across all hosts with access to the LUN, and therefore must be used when creating shared SRs accessible by all hosts in a resource pool.

The same features apply to QLogic iSCSI HBAs.

See Section 3.2.1, “Creating Storage Repositories” for details on creating shared HBA-based FC and iSCSI SRs.

Note

XenServer support for Fibre Channel does not support direct mapping of a LUN to a VM. HBA-based LUNs must be mapped to the host and specified for use in an SR. VDIs within the SR are exposed to VMs as standard block devices.

3.3.12. Citrix StorageLink Gateway (CSLG) SRs

The CSLG storage repository allows use of the Citrix StorageLink service for native access to a range of iSCSI and Fibre Channel arrays and automated fabric/initiator and array configuration features. Installation and configuration of the StorageLink service is required, for more information please see the StorageLink documentation.

Note

Running the StorageLink service in a VM within a resource pool to which the StorageLink service is providing storage is not supported in combination with the XenServer High Availability (HA) features. To use CSLG SRs in combination with HA ensure the StorageLink service is running outside the HA-enabled pool.

CSLG SRs can be created using the xe CLI only. After creation CSLG SRs can be viewed and managed using both the xe CLI and XenCenter.

Because the CSLG SR can be used to access different storage arrays, the exact features available for a given CSLG SR depend on the capabilities of the array. All CSLG SRs use a LUN-per-VDI model where a new LUN is provisioned for each virtual disk. (VDI).

CSLG SRs can co-exist with other SR types on the same storage array hardware, and multiple CSLG SRs can be defined within the same resource pool.

The StorageLink service can be configured using the StorageLink Manager or from within the XenServer control domain using the StorageLink Command Line Interface (CLI). To run the StorageLink (CLI) use the following command, where <hostname> is the name or IP address of the machine running the StorageLink service:

/opt/Citrix/StorageLink/bin/csl \
server=<hostname>[:<port>][,<username>,<password>]

For more information about the StorageLink CLI please see the StorageLink documentation or use the /opt/Citrix/StorageLink/bin/csl help command.

3.3.12.1. Creating a shared StorageLink SR

SRs of type CSLG can only be created by using the xe Command Line Interface (CLI). Once created CSLG SRs can be managed using either XenCenter or the xe CLI.

The device-config parameters for CSLG SRs are:

Parameter name	Description	Optional?
target	The server name or IP address of the machine running the StorageLink service	No
storageSystemId	The storage system ID to use for allocating storage	No
storagePoolId	The storage pool ID within the specified storage system to use for allocating storage	No
username	The username to use for connection to the StorageLink service	Yes ^[a]
password	The password to use for connecting to the StorageLink service	Yes ^[a]
cslport	The port to use for connecting to the StorageLink service	Yes ^[a]
chapuser	The username to use for CHAP authentication	Yes
chappassword	The password to use for CHAP authentication	Yes
protocol	Specifies the storage protocol to use (fc or iscsi) for multi-protocol storage systems. If not specified fc is used if available, otherwise iscsi.	Yes
provision-type	Specifies whether to use thick or thin provisioning (thick or thin); default is thick	Yes
provision-options	Additional provisioning options: Set to `dedup` to use the de-duplication features supported by the storage system	Yes
raid-type	The level of RAID to use for the SR, as supported by the storage array	Yes
^[a]If the username, password, or port configuration of the StorageLink service are changed from the default then the appropriate parameter and value must be specified.

SRs of type cslg support two additional parameters that can be used with storage arrays that support LUN grouping features, such as NetApp flexvols.

sm-config parameters for CSLG SRs:

Parameter name	Description	Optional?
pool-count	Creates the specified number of groups on the array, in which LUNs provisioned within the SR will be created	Yes
physical-size	The total size of the SR in MB. Each pool will be created with a size equal to physical-size divided by pool-count.	Yes ^[a]
^[a]Required when specifying the `sm-config:pool-count parameter`

Note

When a new NetApp SR is created using StorageLink, by default a single FlexVol is created for the SR that contains all LUNs created for the SR. To change this behaviour and specify the number of FlexVols to create and the size of each FlexVol, use the sm-config:pool-size and sm-config:physical-size parameters. sm-config:pool-size specifies the number of FlexVols. sm-config:physical-size specifies the total size of all FlexVols to be created, so that each FlexVol will be of size sm-config:physical-size divided by sm-config:pool-size.

To create a CSLG SR

Install the StorageLink service onto a Windows host or virtual machine
Configure the StorageLink service with the appropriate storage adapters and credentials

Use the sr-probe command with the device-config:target parameter to identify the available storage system IDs

xe sr-probe type=cslg device-config:target=192.168.128.10

<csl__storageSystemInfoList>
    <csl__storageSystemInfo>
        <friendlyName>5001-4380-013C-0240</friendlyName>
        <displayName>HP EVA (5001-4380-013C-0240)</displayName>
        <vendor>HP</vendor>
        <model>EVA</model>
        <serialNum>50014380013C0240</serialNum>
        <storageSystemId>HP__EVA__50014380013C0240</storageSystemId>
        <systemCapabilities>
            <capabilities>PROVISIONING</capabilities>
            <capabilities>MAPPING</capabilities>
            <capabilities>MULTIPLE_STORAGE_POOLS</capabilities>
            <capabilities>DIFF_SNAPSHOT</capabilities>
            <capabilities>CLONE</capabilities>
        </systemCapabilities>
        <protocolSupport>
            <capabilities>FC</capabilities>
        </protocolSupport>
        <csl__snapshotMethodInfoList>
            <csl__snapshotMethodInfo>
                <name>5001-4380-013C-0240</name>
                <displayName></displayName>
                <maxSnapshots>16</maxSnapshots>
                <supportedNodeTypes>
                    <nodeType>STORAGE_VOLUME</nodeType>
                </supportedNodeTypes>
                <snapshotTypeList>
                </snapshotTypeList>
                <snapshotCapabilities>
                </snapshotCapabilities>
            </csl__snapshotMethodInfo>
            <csl__snapshotMethodInfo>
                <name>5001-4380-013C-0240</name>
                <displayName></displayName>
                <maxSnapshots>16</maxSnapshots>
                <supportedNodeTypes>
                    <nodeType>STORAGE_VOLUME</nodeType>
                </supportedNodeTypes>
                <snapshotTypeList>
                    <snapshotType>DIFF_SNAPSHOT</snapshotType>
                </snapshotTypeList>
                <snapshotCapabilities>
                </snapshotCapabilities>
            </csl__snapshotMethodInfo>
            <csl__snapshotMethodInfo>
                <name>5001-4380-013C-0240</name>
                <displayName></displayName>
                <maxSnapshots>16</maxSnapshots>
                <supportedNodeTypes>
                    <nodeType>STORAGE_VOLUME</nodeType>
                </supportedNodeTypes>
                <snapshotTypeList>
                    <snapshotType>CLONE</snapshotType>
                </snapshotTypeList>
               <snapshotCapabilities>
               </snapshotCapabilities>
            </csl__snapshotMethodInfo>
        </csl__snapshotMethodInfoList>
    </csl__storageSystemInfo>
</csl__storageSystemInfoList>

You can use grep to filter the sr-probe output to just the storage pool IDs

xe sr-probe type=cslg device-config:target=192.168.128.10 | grep storageSystemId
        <storageSystemId>EMC__CLARIION__APM00074902515</storageSystemId>
        <storageSystemId>HP__EVA__50014380013C0240</storageSystemId>
        <storageSystemId>NETAPP__LUN__0AD4F00A</storageSystemId>

Add the desired storage system ID to the sr-probe command to identify the storage pools available within the specified storage system

xe sr-probe type=cslg \
device-config:target=192.168.128.10  \ device-config:storageSystemId=HP__EVA__50014380013C0240
<?xml version="1.0" encoding="iso-8859-1"?>
<csl__storagePoolInfoList>
    <csl__storagePoolInfo>
        <displayName>Default Disk Group</displayName>
        <friendlyName>Default Disk Group</friendlyName>
        <storagePoolId>00010710B4080560B6AB08000080000000000400</storagePoolId>
        <parentStoragePoolId></parentStoragePoolId>
        <storageSystemId>HP__EVA__50014380013C0240</storageSystemId>
        <sizeInMB>1957099</sizeInMB>
        <freeSpaceInMB>1273067</freeSpaceInMB>
        <isDefault>No</isDefault>
        <status>0</status>
        <provisioningOptions>
            <supportedRaidTypes>
                <raidType>RAID0</raidType>
                <raidType>RAID1</raidType>
                <raidType>RAID5</raidType>
            </supportedRaidTypes>
            <supportedNodeTypes>
                <nodeType>STORAGE_VOLUME</nodeType>
            </supportedNodeTypes>
        <supportedProvisioningTypes>
        </supportedProvisioningTypes>
        </provisioningOptions>
    </csl__storagePoolInfo>
</csl__storagePoolInfoList>

You can use grep to filter the sr-probe output to just the storage pool IDs

xe sr-probe type=cslg \
device-config:target=192.168.128.10 \
device-config:storageSystemId=HP__EVA__50014380013C0240 \
| grep storagePoolId
<storagePoolId>00010710B4080560B6AB08000080000000000400</storagePoolId>

Create the SR specifying the desired storage system and storage pool IDs

xe sr-create type=cslg name-label=CSLG_EVA_1 shared=true \
device-config:target=192.168.128.10 \
device-config:storageSystemId=HP__EVA__50014380013C0240 \
device-config:storagePoolId=00010710B4080560B6AB08000080000000000400

3.4. Managing Storage Repositories

This section covers various operations required in the ongoing management of Storage Repositories (SRs).

3.4.1. Destroying or forgetting a SR

You can destroy an SR, which actually deletes the contents of the SR from the physical media. Alternatively you can forget an SR, which allows you to re-attach the SR, for example, to another XenServer host, without removing any of the SR contents. In both cases, the PBD of the SR must first be unplugged. Forgetting an SR is the equivalent of the SR Detach operation within XenCenter.

Unplug the PBD to detach the SR from the corresponding XenServer host:
```
xe pbd-unplug uuid=<pbd_uuid>
```
To destroy the SR, which deletes both the SR and corresponding PBD from the XenServer host database and deletes the SR contents from the physical media:
```
xe sr-destroy uuid=<sr_uuid>
```
Or, to forget the SR, which removes the SR and corresponding PBD from the XenServer host database but leaves the actual SR contents intact on the physical media:
```
xe sr-forget uuid=<sr_uuid>
```

Note

It might take some time for the software object corresponding to the SR to be garbage collected.

3.4.2. Introducing an SR

Introducing an SR that has been forgotten requires introducing an SR, creating a PBD, and manually plugging the PBD to the appropriate XenServer hosts to activate the SR.

The following example introduces a SR of type lvmoiscsi.

Probe the existing SR to determine its UUID:

xe sr-probe type=lvmoiscsi device-config:target=<192.168.1.10> \ 
device-config:targetIQN=<192.168.1.10:filer1> \
device-config:SCSIid=<149455400000000000000000002000000b70200000f000000>

Introduce the existing SR UUID returned from the sr-probe command. The UUID of the new SR is returned:

xe sr-introduce content-type=user name-label=<"Example Shared LVM over iSCSI SR">
shared=true uuid=<valid_sr_uuid> type=lvmoiscsi

Create a PBD to accompany the SR. The UUID of the new PBD is returned:

xe pbd-create type=lvmoiscsi host-uuid=<valid_uuid> sr-uuid=<valid_sr_uuid> \
device-config:target=<192.168.0.1> \
device-config:targetIQN=<192.168.1.10:filer1> \
device-config:SCSIid=<149455400000000000000000002000000b70200000f000000>

Plug the PBD to attach the SR:
```
xe pbd-plug uuid=<pbd_uuid>
```
Verify the status of the PBD plug. If successful the currently-attached property will be true:
```
xe pbd-list sr-uuid=<sr_uuid>
```

Note

Steps 3 through 5 must be performed for each host in the resource pool, and can also be performed using the Repair Storage Repository function in XenCenter.

3.4.3. Resizing an SR

If you have resized the LUN on which a iSCSI or HBA SR is based, use the following procedures to reflect the size change in XenServer:

iSCSI SRs - unplug all PBDs on the host that reference LUNs on the same target. This is required to reset the iSCSI connection to the target, which in turn will allow the change in LUN size to be recognized when the PBDs are replugged.
HBA SRs - reboot the host.

Note

In previous versions of XenServer explicit commands were required to resize the physical volume group of iSCSI and HBA SRs. These commands are now issued as part of the PBD plug operation and are no longer required.

3.4.4. Converting local Fibre Channel SRs to shared SRs

Use the xe CLI and the XenCenter Repair Storage Repository feature to convert a local FC SR to a shared FC SR:

Upgrade all hosts in the resource pool to XenServer 5.5.0.
Ensure all hosts in the pool have the SR's LUN zoned appropriately. See Section 3.2.5, “Probing an SR” for details on using the sr-probe command to verify the LUN is present on each host.

Convert the SR to shared:

xe sr-param-set shared=true uuid=<local_fc_sr>

Within XenCenter the SR is moved from the host level to the pool level, indicating that it is now shared. The SR will be marked with a red exclamation mark to show that it is not currently plugged on all hosts in the pool.
Select the SR and then select the Storage > Repair Storage Repository menu option.
Click Repair to create and plug a PBD for each host in the pool.

3.4.5. Moving Virtual Disk Images (VDIs) between SRs

The set of VDIs associated with a VM can be copied from one SR to another to accommodate maintenance requirements or tiered storage configurations. XenCenter provides the ability to copy a VM and all of its VDIs to the same or a different SR, and a combination of XenCenter and the xe CLI can be used to copy individual VDIs.

3.4.5.1. Copying all of a VM's VDIs to a different SR

The XenCenter Copy VM function creates copies of all VDIs for a selected VM on the same or a different SR. The source VM and VDIs are not affected by default. To move the VM to the selected SR rather than creating a copy, select the Remove original VM option in the Copy Virtual Machine dialog box.

Shutdown the VM.
Within XenCenter select the VM and then select the VM > Copy VM menu option.
Select the desired target SR.

3.4.5.2. Copying individual VDIs to a different SR

A combination of the xe CLI and XenCenter can be used to copy individual VDIs between SRs.

Shutdown the VM.
Use the xe CLI to identify the UUIDs of the VDIs to be moved. If the VM has a DVD drive its vdi-uuid will be listed as <not in database> and can be ignored.
```
xe vbd-list vm-uuid=<valid_vm_uuid>
```
Note
The vbd-list command displays both the VBD and VDI UUIDs. Be sure to record the VDI UUIDs rather than the VBD UUIDs.
In XenCenter select the VM's Storage tab. For each VDI to be moved, select the VDI and click the Detach button. This step can also be done using the vbd-destroy command.
Note
If you use the vbd-destroy command to detach the VDI UUIDs, be sure to first check if the VBD has the parameter other-config:owner set to true. If so, set it to false. Issuing the vbd-destroy command with other-config:owner=true will also destroy the associated VDI.
Use the vdi-copy command to copy each of the VM's VDIs to be moved to the desired SR.
```
xe vdi-copy uuid=<valid_vdi_uuid> sr-uuid=<valid_sr_uuid>
```
Within XenCenter select the VM's Storage tab. Click the Attach button and select the VDIs from the new SR. This step can also be done use the vbd-create command.
To delete the original VDIs, within XenCenter select the Storage tab of the original SR. The original VDIs will be listed with an empty value for the VM field and can be deleted with the Delete button.

3.4.6. Adjusting the disk IO scheduler

For general performance, the default disk scheduler noop is applied on all new SR types. The noop scheduler provides the fairest performance for competing VMs accessing the same device. To apply disk QoS (see Section 3.5, “Virtual disk QoS settings”) it is necessary to override the default setting and assign the cfq disk scheduler to the SR. The corresponding PBD must be unplugged and re-plugged for the scheduler parameter to take effect. The disk scheduler can be adjusted using the following command:

xe sr-param-set other-config:scheduler=noop|cfq|anticipatory|deadline \
uuid=<valid_sr_uuid>

Note

This will not effect EqualLogic, NetApp or NFS storage.

3.5. Virtual disk QoS settings

Virtual disks have an optional I/O priority Quality of Service (QoS) setting. This setting can be applied to existing virtual disks using the xe CLI as described in this section.

In the shared SR case, where multiple hosts are accessing the same LUN, the QoS setting is applied to VBDs accessing the LUN from the same host. QoS is not applied across hosts in the pool.

Before configuring any QoS parameters for a VBD, ensure that the disk scheduler for the SR has been set appropriately. See Section 3.4.6, “Adjusting the disk IO scheduler” for details on how to adjust the scheduler. The scheduler parameter must be set to cfq on the SR for which the QoS is desired.

Note

Remember to set the scheduler to cfq on the SR, and to ensure that the PBD has been re-plugged in order for the scheduler change to take effect.

The first parameter is qos_algorithm_type. This parameter needs to be set to the value ionice, which is the only type of QoS algorithm supported for virtual disks in this release.

The QoS parameters themselves are set with key/value pairs assigned to the qos_algorithm_param parameter. For virtual disks, qos_algorithm_param takes a sched key, and depending on the value, also requires a class key.

Possible values of qos_algorithm_param:sched are:

sched=rt or sched=real-time sets the QoS scheduling parameter to real time priority, which requires a class parameter to set a value
sched=idle sets the QoS scheduling parameter to idle priority, which requires no class parameter to set any value
sched=<anything> sets the QoS scheduling parameter to best effort priority, which requires a class parameter to set a value

The possible values for class are:

One of the following keywords: highest, high, normal, low, lowest
an integer between 0 and 7, where 7 is the highest priority and 0 is the lowest, so that, for example, I/O requests with a priority of 5, will be given priority over I/O requests with a priority of 2.

To enable the disk QoS settings, you also need to set the other-config:scheduler to cfq and replug PBDs for the storage in question.

For example, the following CLI commands set the virtual disk's VBD to use real time priority 5:

xe vbd-param-set uuid=<vbd_uuid> qos_algorithm_type=ionice
xe vbd-param-set uuid=<vbd_uuid> qos_algorithm_params:sched=rt
xe vbd-param-set uuid=<vbd_uuid> qos_algorithm_params:class=5
xe sr-param-set uuid=<sr_uuid> other-config:scheduler-cfq
xe pbd-plug uuid=<pbd_uuid>

Chapter 4. Networking

This chapter discusses how physical network interface cards (NICs) in XenServer hosts are used to enable networking within Virtual Machines (VMs). XenServer supports up to 6 physical network interfaces (or up to 6 pairs of bonded network interfaces) per XenServer host and up to 7 virtual network interfaces per VM.

Note

XenServer provides automated configuration and management of NICs using the xe command line interface (CLI). Unlike previous XenServer versions, the host networking configuration files should not be edited directly in most cases; where a CLI command is available, do not edit the underlying files.

If you are already familiar with XenServer networking concepts, you may want to skip ahead to one of the following sections:

For procedures on how to create networks for standalone XenServer hosts, see Section 4.2.1, “Creating networks in a standalone server”.
For procedures on how to create networks for XenServer hosts that are configured in a resource pool, see Section 4.2.2, “Creating networks in resource pools”.
For procedures on how to create VLANs for XenServer hosts, either standalone or part of a resource pool, see Section 4.2.3, “Creating VLANs”.
For procedures on how to create bonds for standalone XenServer hosts, see Section 4.2.4, “Creating NIC bonds on a standalone host”.
For procedures on how to create bonds for XenServer hosts that are configured in a resource pool, see Section 4.2.5, “Creating NIC bonds in resource pools”.

4.1. XenServer networking overview

This section describes the general concepts of networking in the XenServer environment.

Note

Some networking options have different behaviors when used with standalone XenServer hosts compared to resource pools. This chapter contains sections on general information that applies to both standalone hosts and pools, followed by specific information and procedures for each.

4.1.1. Network objects

There are three types of server-side software objects which represent networking entities. These objects are:

A PIF, which represents a physical network interface on a XenServer host. PIF objects have a name and description, a globally unique UUID, the parameters of the NIC that they represent, and the network and server they are connected to.
A VIF, which represents a virtual interface on a Virtual Machine. VIF objects have a name and description, a globally unique UUID, and the network and VM they are connected to.
A network, which is a virtual Ethernet switch on a XenServer host. Network objects have a name and description, a globally unique UUID, and the collection of VIFs and PIFs connected to them.

Both XenCenter and the xe CLI allow configuration of networking options, control over which NIC is used for management operations, and creation of advanced networking features such as virtual local area networks (VLANs) and NIC bonds.

From XenCenter much of the complexity of XenServer networking is hidden. There is no mention of PIFs for XenServer hosts nor VIFs for VMs.

4.1.2. Networks

Each XenServer host has one or more networks, which are virtual Ethernet switches. Networks without an association to a PIF are considered internal, and can be used to provide connectivity only between VMs on a given XenServer host, with no connection to the outside world. Networks with a PIF association are considered external, and provide a bridge between VIFs and the PIF connected to the network, enabling connectivity to resources available through the PIF's NIC.

4.1.3. VLANs

Virtual Local Area Networks (VLANs), as defined by the IEEE 802.1Q standard, allow a single physical network to support multiple logical networks. XenServer hosts can work with VLANs in multiple ways.

Note

All supported VLAN configurations are equally applicable to pools and standalone hosts, and bonded and non-bonded configurations.

4.1.3.1. Using VLANs with host management interfaces

Switch ports configured to perform 802.1Q VLAN tagging/untagging, commonly referred to as ports with a native VLAN or as access mode ports, can be used with XenServer management interfaces to place management traffic on a desired VLAN. In this case the XenServer host is unaware of any VLAN configuration.

XenServer management interfaces cannot be assigned to a XenServer VLAN via a trunk port.

4.1.3.2. Using VLANs with virtual machines

Switch ports configured as 802.1Q VLAN trunk ports can be used in combination with the XenServer VLAN features to connect guest virtual network interfaces (VIFs) to specific VLANs. In this case the XenServer host performs the VLAN tagging/untagging functions for the guest, which is unaware of any VLAN configuration.

XenServer VLANs are represented by additional PIF objects representing VLAN interfaces corresponding to a specified VLAN tag. XenServer networks can then be connected to the PIF representing the physical NIC to see all traffic on the NIC, or to a PIF representing a VLAN to see only the traffic with the specified VLAN tag.

For procedures on how to create VLANs for XenServer hosts, either standalone or part of a resource pool, see Section 4.2.3, “Creating VLANs”.

4.1.3.3. Using VLANs with dedicated storage NICs

Dedicated storage NICs can be configured to use native VLAN / access mode ports as described above for management interfaces, or with trunk ports and XenServer VLANs as described above for virtual machines. To configure dedicated storage NICs, see Section 4.2.6, “Configuring a dedicated storage NIC”.

4.1.3.4. Combining management interfaces and guest VLANs on a single host NIC

A single switch port can be configured with both trunk and native VLANs, allowing one host NIC to be used for a management interface (on the native VLAN) and for connecting guest VIFs to specific VLAN IDs.

4.1.4. NIC bonds

NIC bonds can improve XenServer host resiliency by using two physical NICs as if they were one. If one NIC within the bond fails the host's network traffic will automatically be routed over the second NIC. NIC bonds work in an active/active mode, with traffic balanced between the bonded NICs.

XenServer NIC bonds completely subsume the underlying physical devices (PIFs). In order to activate a bond the underlying PIFs must not be in use, either as the management interface for the host or by running VMs with VIFs attached to the networks associated with the PIFs.

XenServer NIC bonds are represented by additional PIFs. The bond PIF can then be connected to a XenServer network to allow VM traffic and host management functions to occur over the bonded NIC. The exact steps to use to create a NIC bond depend on the number of NICs in your host, and whether the management interface of the host is assigned to a PIF to be used in the bond.

XenServer supports Source Level Balancing (SLB) NIC bonding. SLB bonding:

is an active/active mode, but only supports load-balancing of VM traffic across the physical NICs
provides fail-over support for all other traffic types
does not require switch support for Etherchannel or 802.3ad (LACP)
load balances traffic between multiple interfaces at VM granularity by sending traffic through different interfaces based on the source MAC address of the packet
is derived from the open source ALB mode and reuses the ALB capability to dynamically re-balance load across interfaces

Any given VIF will only use one of the links in the bond at a time. At startup no guarantees are made about the affinity of a given VIF to a link in the bond. However, for VIFs with high throughput, periodic rebalancing ensures that the load on the links is approximately equal.

API Management traffic can be assigned to a XenServer bond interface and will be automatically load-balanced across the physical NICs.

XenServer bonded PIFs do not require IP configuration for the bond when used for guest traffic. This is because the bond operates at Layer 2 of the OSI, the data link layer, and no IP addressing is used at this layer. When used for non-guest traffic (to connect to it with XenCenter for management, or to connect to shared network storage), one IP configuration is required per bond. (Incidentally, this is true of unbonded PIFs as well, and is unchanged from XenServer 4.1.0.)

Gratuitous ARP packets are sent when assignment of traffic changes from one interface to another as a result of fail-over.

Re-balancing is provided by the existing ALB re-balance capabilities: the number of bytes going over each slave (interface) is tracked over a given period. When a packet is to be sent that contains a new source MAC address it is assigned to the slave interface with the lowest utilization. Traffic is re-balanced every 10 seconds.

Note

Bonding is set up with an Up Delay of 31000ms and a Down Delay of 200ms. The seemingly long Up Delay is purposeful because of the time taken by some switches to actually start routing traffic. Without it, when a link comes back after failing, the bond might rebalance traffic onto it before the switch is ready to pass traffic. If you want to move both connections to a different switch, move one, then wait 31 seconds for it to be used again before moving the other.

4.1.5. Initial networking configuration

The XenServer host networking configuration is specified during initial host installation. Options such as IP address configuration (DHCP/static), the NIC used as the management interface, and hostname are set based on the values provided during installation.

When a XenServer host has a single NIC, the follow configuration is present after installation:

a single PIF is created corresponding to the host's single NIC
the PIF is configured with the IP addressing options specified during installation and to enable management of the host
the PIF is set for use in host management operations
a single network, network 0, is created
network 0 is connected to the PIF to enable external connectivity to VMs

When a host has multiple NICs the configuration present after installation depends on which NIC is selected for management operations during installation:

PIFs are created for each NIC in the host
the PIF of the NIC selected for use as the management interface is configured with the IP addressing options specified during installation
a network is created for each PIF ("network 0", "network 1", etc.)
each network is connected to one PIF
the IP addressing options of all other PIFs are left unconfigured

In both cases the resulting networking configuration allows connection to the XenServer host by XenCenter, the xe CLI, and any other management software running on separate machines via the IP address of the management interface. The configuration also provides external networking for VMs created on the host.

The PIF used for management operations is the only PIF ever configured with an IP address. External networking for VMs is achieved by bridging PIFs to VIFs using the network object which acts as a virtual Ethernet switch.

The steps required for networking features such as VLANs, NIC bonds, and dedicating a NIC to storage traffic are covered in the following sections.

4.2. Managing networking configuration

Some of the network configuration procedures in this section differ depending on whether you are configuring a stand-alone server or a server that is part of a resource pool.

4.2.1. Creating networks in a standalone server

Because external networks are created for each PIF during host installation, creating additional networks is typically only required to:

use an internal network
support advanced operations such as VLANs or NIC bonding

To add or remove networks using XenCenter, refer to the XenCenter online Help.

To add a new network using the CLI

Open the XenServer host text console.
Create the network with the network-create command, which returns the UUID of the newly created network:
```
xe network-create name-label=<mynetwork>
```

At this point the network is not connected to a PIF and therefore is internal.

4.2.2. Creating networks in resource pools

All XenServer hosts in a resource pool should have the same number of physical network interface cards (NICs), although this requirement is not strictly enforced when a XenServer host is joined to a pool.

Having the same physical networking configuration for XenServer hosts within a pool is important because all hosts in a pool share a common set of XenServer networks. PIFs on the individual hosts are connected to pool-wide networks based on device name. For example, all XenServer hosts in a pool with an eth0 NIC will have a corresponding PIF plugged into the pool-wide Network 0 network. The same will be true for hosts with eth1 NICs and Network 1, as well as other NICs present in at least one XenServer host in the pool.

If one XenServer host has a different number of NICs than other hosts in the pool, complications can arise because not all pool networks will be valid for all pool hosts. For example, if hosts host1 and host2 are in the same pool and host1 has four NICs while host2 only has two, only the networks connected to PIFs corresponding to eth0 and eth1 will be valid on host2. VMs on host1 with VIFs connected to networks corresponding to eth2 and eth3 will not be able to migrate to host host2.

All NICs of all XenServer hosts within a resource pool must be configured with the same MTU size.

4.2.3. Creating VLANs

For servers in a resource pool, you can use the pool-vlan-create command. This command creates the VLAN and automatically creates and plugs in the required PIFs on the hosts in the pool. See Section 8.4.22.2, “pool-vlan-create” for more information.

To connect a network to an external VLAN using the CLI

Open the XenServer host text console.

Create a new network for use with the VLAN. The UUID of the new network is returned:

xe network-create name-label=network5

Use the pif-list command to find the UUID of the PIF corresponding to the physical NIC supporting the desired VLAN tag. The UUIDs and device names of all PIFs are returned, including any existing VLANs:

xe pif-list

Create a VLAN object specifying the desired physical PIF and VLAN tag on all VMs to be connected to the new VLAN. A new PIF will be created and plugged into the specified network. The UUID of the new PIF object is returned.

xe vlan-create network-uuid=<network_uuid> pif-uuid=<pif_uuid> vlan=5

Attach VM VIFs to the new network. See Section 4.2.1, “Creating networks in a standalone server” for more details.

4.2.4. Creating NIC bonds on a standalone host

Citrix recommends using XenCenter to create NIC bonds. For details, refer to the XenCenter help.

This section describes how to use the xe CLI to create bonded NIC interfaces on a standalone XenServer host. See Section 4.2.5, “Creating NIC bonds in resource pools” for details on using the xe CLI to create NIC bonds on XenServer hosts that comprise a resource pool.

4.2.4.1. Creating a NIC bond on a dual-NIC host

Creating a bond on a dual-NIC host implies that the PIF/NIC currently in use as the management interface for the host will be subsumed by the bond. The additional steps required to move the management interface to the bond PIF are included.

Bonding two NICs together

Use XenCenter or the vm-shutdown command to shut down all VMs on the host, thereby forcing all VIFs to be unplugged from their current networks. The existing VIFs will be invalid after the bond is enabled.

xe vm-shutdown uuid=<vm_uuid>

Use the network-create command to create a new network for use with the bonded NIC. The UUID of the new network is returned:

xe network-create name-label=<bond0>

Use the pif-list command to determine the UUIDs of the PIFs to use in the bond:

xe pif-list

Use the bond-create command to create the bond by specifying the newly created network UUID and the UUIDs of the PIFs to be bonded separated by commas. The UUID for the bond is returned:
```
xe bond-create network-uuid=<network_uuid> pif-uuids=<pif_uuid_1>,<pif_uuid_2>
```
Note
See Section 4.2.4.2, “Controlling the MAC address of the bond” for details on controlling the MAC address used for the bond PIF.
Use the pif-list command to determine the UUID of the new bond PIF:
```
xe pif-list device=<bond0>
```
Use the pif-reconfigure-ip command to configure the desired management interface IP address settings for the bond PIF. See Chapter 8, Command line interface for more detail on the options available for the pif-reconfigure-ip command.
```
xe pif-reconfigure-ip uuid=<bond_pif_uuid> mode=DHCP
```
Use the host-management-reconfigure command to move the management interface from the existing physical PIF to the bond PIF. This step will activate the bond:
```
xe host-management-reconfigure pif-uuid=<bond_pif_uuid>
```
Use the pif-reconfigure-ip command to remove the IP address configuration from the non-bonded PIF previously used for the management interface. This step is not strictly necessary but might help reduce confusion when reviewing the host networking configuration.
```
xe pif-reconfigure-ip uuid=<old_management_pif_uuid> mode=None
```
Move existing VMs to the bond network using the vif-destroy and vif-create commands. This step can also be completed using XenCenter by editing the VM configuration and connecting the existing VIFs of a VM to the bond network.
Restart the VMs shut down in step 1.

4.2.4.2. Controlling the MAC address of the bond

Creating a bond on a dual-NIC host implies that the PIF/NIC currently in use as the management interface for the host will be subsumed by the bond. If DHCP is used to supply IP addresses to the host in most cases the MAC address of the bond should be the same as the PIF/NIC currently in use, allowing the IP address of the host received from DHCP to remain unchanged.

The MAC address of the bond can be changed from PIF/NIC currently in use for the management interface, but doing so will cause existing network sessions to the host to be dropped when the bond is enabled and the MAC/IP address in use changes.

The MAC address to be used for a bond can be controlled in two ways:

an optional mac parameter can be specified in the bond-create command. Using this parameter, the bond MAC address can be set to any arbitrary address.
If the mac parameter is not specified, the MAC address of the first PIF listed in the pif-uuids parameter is used for the bond.

4.2.4.3. Reverting NIC bonds

If reverting a XenServer host to a non-bonded configuration, be aware of the following requirements:

As when creating a bond, all VMs with VIFs on the bond must be shut down prior to destroying the bond. After reverting to a non-bonded configuration, reconnect the VIFs to an appropriate network.
Move the management interface to another PIF using the pif-reconfigure-ip and host-management-reconfigure commands prior to issuing the bond-destroy command, otherwise connections to the host (including XenCenter) will be dropped.

4.2.5. Creating NIC bonds in resource pools

Whenever possible, create NIC bonds as part of initial resource pool creation prior to joining additional hosts to the pool or creating VMs. Doing so allows the bond configuration to be automatically replicated to hosts as they are joined to the pool and reduces the number of steps required. Adding a NIC bond to an existing pool requires creating the bond configuration manually on the master and each of the members of the pool. Adding a NIC bond to an existing pool after VMs have been installed is also a disruptive operation, as all VMs in the pool must be shut down.

Citrix recommends using XenCenter to create NIC bonds. For details, refer to the XenCenter help.

This section describes using the xe CLI to create bonded NIC interfaces on XenServer hosts that comprise a resource pool. See Section 4.2.4.1, “Creating a NIC bond on a dual-NIC host” for details on using the xe CLI to create NIC bonds on a standalone XenServer host.

Warning

Do not attempt to create network bonds while HA is enabled. The process of bond creation will disturb the in-progress HA heartbeating and cause hosts to self-fence (shut themselves down); subsequently they will likely fail to reboot properly and will need the host-emergency-ha-disable command to recover.

4.2.5.1. Adding NIC bonds to new resource pools

Select the host you want to be the master. The master host belongs to an unnamed pool by default. To create a resource pool with the CLI, rename the existing nameless pool:

xe pool-param-set name-label=<"New Pool"> uuid=<pool_uuid>

Create the NIC bond on the master as follows:
1. Use the bond-create command to create the bond, specifying the network UUID created in step a and the UUIDs of the PIFs to be bonded, separated by commas. The UUID for the bond is returned:
```
xe bond-create network-uuid=<network_uuid> pif-uuids=<pif_uuid_1>,<pif_uuid_2>
```
  Note
  See Section 4.2.4.2, “Controlling the MAC address of the bond” for details on controlling the MAC address used for the bond PIF.
2. Use the pif-list command to determine the UUID of the new bond PIF:
```
xe pif-list  network-uuid=<network_uuid>
```
3. Use the pif-reconfigure-ip command to configure the desired management interface IP address settings for the bond PIF. See Chapter 8, Command line interface, for more detail on the options available for the pif-reconfigure-ip command.
```
xe pif-reconfigure-ip uuid=<bond_pif_uuid> mode=DHCP
```
4. Use the host-management-reconfigure command to move the management interface from the existing physical PIF to the bond PIF. This step will activate the bond:
```
xe host-management-reconfigure pif-uuid=<bond_pif_uuid>
```
5. Use the pif-reconfigure-ip command to remove the IP address configuration from the non-bonded PIF previously used for the management interface. This step is not strictly necessary but might help reduce confusion when reviewing the host networking configuration.
```
xe pif-reconfigure-ip uuid=<old_management_pif_uuid> mode=None
```
Open a console on a host that you want to join to the pool and run the command:
```
xe pool-join master-address=<host1> master-username=root master-password=<password>
```
The network and bond information is automatically replicated to the new host. However, the management interface is not automatically moved from the host NIC to the bonded NIC. Move the management interface on the host to enable the bond as follows:
1. Use the host-list command to find the UUID of the host being configured:
```
xe host-list
```
2. Use the pif-list command to determine the UUID of bond PIF on the new host. Include the host-uuid parameter to list only the PIFs on the host being configured:
```
xe pif-list network-name-label=<network_name> host-uuid=<host_uuid>
```
3. Use the pif-reconfigure-ip command to configure the desired management interface IP address settings for the bond PIF. See Chapter 8, Command line interface, for more detail on the options available for the pif-reconfigure-ip command. This command must be run directly on the host:
```
xe pif-reconfigure-ip uuid=<bond_pif_uuid> mode=DHCP
```
4. Use the host-management-reconfigure command to move the management interface from the existing physical PIF to the bond PIF. This step activates the bond. This command must be run directly on the host:
```
xe host-management-reconfigure pif-uuid=<bond_pif_uuid>
```
5. Use the pif-reconfigure-ip command to remove the IP address configuration from the non-bonded PIF previously used for the management interface. This step is not strictly necessary but may help reduce confusion when reviewing the host networking configuration. This command must be run directly on the host server:
```
xe pif-reconfigure-ip uuid=<old_mgmt_pif_uuid> mode=None
```
For each additional host you want to join to the pool, repeat steps 3 and 4 to move the management interface on the host and to enable the bond.

4.2.5.2. Adding NIC bonds to an existing pool

Warning

Do not attempt to create network bonds while HA is enabled. The process of bond creation disturbs the in-progress HA heartbeating and causes hosts to self-fence (shut themselves down); subsequently they will likely fail to reboot properly and you will need to run the host-emergency-ha-disable command to recover them.

Note

If you are not using XenCenter for NIC bonding, the quickest way to create pool-wide NIC bonds is to create the bond on the master, and then restart the other pool members. Alternately you can use the service xapi restart command. This causes the bond and VLAN settings on the master to be inherited by each host. The management interface of each host must, however, be manually reconfigured.

When adding a NIC bond to an existing pool, the bond must be manually created on each host in the pool. The steps below can be used to add NIC bonds on both the pool master and other hosts with the following requirements:

All VMs in the pool must be shut down
Add the bond to the pool master first, and then to other hosts.
The bond-create, host-management-reconfigure and host-management-disable commands affect the host on which they are run and so are not suitable for use on one host in a pool to change the configuration of another. Run these commands directly on the console of the host to be affected.

To add NIC bonds to the pool master and other hosts

Use the network-create command to create a new pool-wide network for use with the bonded NICs. This step should only be performed once per pool. The UUID of the new network is returned.

xe network-create name-label=<bond0>

Use XenCenter or the vm-shutdown command to shut down all VMs in the host pool to force all existing VIFs to be unplugged from their current networks. The existing VIFs will be invalid after the bond is enabled.

xe vm-shutdown uuid=<vm_uuid>

Use the host-list command to find the UUID of the host being configured:

xe host-list

Use the pif-list command to determine the UUIDs of the PIFs to use in the bond. Include the host-uuid parameter to list only the PIFs on the host being configured:

xe pif-list host-uuid=<host_uuid>

Use the bond-create command to create the bond, specifying the network UUID created in step 1 and the UUIDs of the PIFs to be bonded, separated by commas. The UUID for the bond is returned.
```
xe bond-create network-uuid=<network_uuid> pif-uuids=<pif_uuid_1>,<pif_uuid_2>
```
Note
See Section 4.2.4.2, “Controlling the MAC address of the bond” for details on controlling the MAC address used for the bond PIF.
Use the pif-list command to determine the UUID of the new bond PIF. Include the host-uuid parameter to list only the PIFs on the host being configured:
```
xe pif-list device=bond0 host-uuid=<host_uuid>
```
Use the pif-reconfigure-ip command to configure the desired management interface IP address settings for the bond PIF. See Chapter 8, Command line interface for more detail on the options available for the pif-reconfigure-ip command. This command must be run directly on the host:
```
xe pif-reconfigure-ip uuid=<bond_pif_uuid> mode=DHCP
```
Use the host-management-reconfigure command to move the management interface from the existing physical PIF to the bond PIF. This step will activate the bond. This command must be run directly on the host:
```
xe host-management-reconfigure pif-uuid=<bond_pif_uuid>
```
Use the pif-reconfigure-ip command to remove the IP address configuration from the non-bonded PIF previously used for the management interface. This step is not strictly necessary, but might help reduce confusion when reviewing the host networking configuration. This command must be run directly on the host:
```
xe pif-reconfigure-ip uuid=<old_management_pif_uuid> mode=None
```
Move existing VMs to the bond network using the vif-destroy and vif-create commands. This step can also be completed using XenCenter by editing the VM configuration and connecting the existing VIFs of the VM to the bond network.
Repeat steps 3 - 10 for other hosts.
Restart the VMs previously shut down.

4.2.6. Configuring a dedicated storage NIC

XenServer allows use of either XenCenter or the xe CLI to configure and dedicate a NIC to specific functions, such as storage traffic.

Assigning a NIC to a specific function will prevent the use of the NIC for other functions such as host management, but requires that the appropriate network configuration be in place in order to ensure the NIC is used for the desired traffic. For example, to dedicate a NIC to storage traffic the NIC, storage target, switch, and/or VLAN must be configured such that the target is only accessible over the assigned NIC. This allows use of standard IP routing to control how traffic is routed between multiple NICs within a XenServer.

Note

Before dedicating a network interface as a storage interface for use with iSCSI or NFS SRs, ensure that the dedicated interface uses a separate IP subnet which is not routable from the main management interface. If this is not enforced, then storage traffic may be directed over the main management interface after a host reboot, due to the order in which network interfaces are initialized.

To assign NIC functions using the xe CLI

Ensure that the PIF is on a separate subnet, or routing is configured to suit your network topology in order to force the desired traffic over the selected PIF.
Setup an IP configuration for the PIF, adding appropriate values for the mode parameter and if using static IP addressing the IP, netmask, gateway, and DNS parameters:
```
xe pif-reconfigure-ip mode=<DHCP | Static> uuid=<pif-uuid>
```

Set the PIF's disallow-unplug parameter to true:

xe pif-param-set disallow-unplug=true uuid=<pif-uuid>

xe pif-param-set other-config:management_purpose="Storage" uuid=<pif-uuid>

If you want to use a storage interface that can be routed from the management interface also (bearing in mind that this configuration is not recommended), then you have two options:

After a host reboot, ensure that the storage interface is correctly configured, and use the xe pbd-unplug and xe pbd-plug commands to reinitialize the storage connections on the host. This will restart the storage connection and route it over the correct interface.
Alternatively, you can use xe pif-forget to remove the interface from the XenServer database, and manually configure it in the control domain. This is an advanced option and requires you to be familiar with how to manually configure Linux networking.

4.2.7. Controlling Quality of Service (QoS)

Citrix Essentials for XenServer allows an optional Quality of Service (QoS) value to be set on VM virtual network interfaces (VIFs) using the CLI. The supported QoS algorithm type is rate limiting, specified as a maximum transfer rate for the VIF in Kb per second.

For example, to limit a VIF to a maximum transfer rate of 100kb/s, use the vif-param-set command:

xe vif-param-set uuid=<vif_uuid> qos_algorithm_type=ratelimit
xe vif-param-set uuid=<vif_uuid> qos_algorithm_params:kbps=100

4.2.8. Changing networking configuration options

This section discusses how to change the networking configuration of a XenServer host. This includes:

changing the hostname
adding or removing DNS servers
changing IP addresses
changing which NIC is used as the management interface
adding a new physical NIC to the server

4.2.8.1. Hostname

The system hostname is defined in the pool-wide database and modified using the xe host-set-hostname-live CLI command as follows:

xe host-set-hostname-live uuid=<host_uuid> host-name=example

The underlying control domain hostname changes dynamically to reflect the new hostname.

4.2.8.2. DNS servers

To add or remove DNS servers in the IP addressing configuration of a XenServer host, use the pif-reconfigure-ip command. For example, for a PIF with a static IP:

pif-reconfigure-ip uuid=<pif_uuid> mode=static DNS=<new_dns_ip>

4.2.8.3. Changing IP address configuration for a standalone host

Network interface configuration can be changed using the xe CLI. The underlying network configuration scripts should not be modified directly.

To modify the IP address configuration of a PIF, use the pif-reconfigure-ip CLI command. See Section 8.4.11.4, “pif-reconfigure-ip” for details on the parameters of the pif-reconfigure-ip command.

Note

See Section 4.2.8.4, “Changing IP address configuration in resource pools” for details on changing host IP addresses in resource pools.

4.2.8.4. Changing IP address configuration in resource pools

XenServer hosts in resource pools have a single management IP address used for management and communication to and from other hosts in the pool. The steps required to change the IP address of a host's management interface are different for master and other hosts.

Note

Caution should be used when changing the IP address of a server, and other networking parameters. Depending upon the network topology and the change being made, connections to network storage may be lost. If this happens the storage must be replugged using the Repair Storage function in XenCenter, or the pbd-plug command using the CLI. For this reason, it may be advisable to migrate VMs away from the server before changing its IP configuration.

Changing the IP address of a pool member host

Use the pif-reconfigure-ip CLI command to set the IP address as desired. See Chapter 8, Command line interface for details on the parameters of the pif-reconfigure-ip command:
```
xe pif-reconfigure-ip uuid=<pif_uuid> mode=DHCP
```
Use the host-list CLI command to confirm that the member host has successfully reconnected to the master host by checking that all the other XenServer hosts in the pool are visible:
```
xe host-list
```

Changing the IP address of the master XenServer host requires additional steps because each of the member hosts uses the advertised IP address of the pool master for communication and will not know how to contact the master when its IP address changes.

Whenever possible, use a dedicated IP address that is not likely to change for the lifetime of the pool for pool masters.

To change the IP address of a pool master host

Use the pif-reconfigure-ip CLI command to set the IP address as desired. See Chapter 8, Command line interface for details on the parameters of the pif-reconfigure-ip command:
```
xe pif-reconfigure-ip uuid=<pif_uuid> mode=DHCP
```
When the IP address of the pool master host is changed, all member hosts will enter into an emergency mode when they fail to contact the master host.
On the master XenServer host, use the pool-recover-slaves command to force the master to contact each of the member hosts and inform them of the new master IP address:
```
xe pool-recover-slaves
```

Refer to Section 6.4.2, “Master failures” for more information on emergency mode.

4.2.8.5. Management interface

When XenServer is installed on a host with multiple NICs, one NIC is selected for use as the management interface. The management interface is used for XenCenter connections to the host and for host-to-host communication.

To change the NIC used for the management interface

Use the pif-list command to determine which PIF corresponds to the NIC to be used as the management interface. The UUID of each PIF is returned.

xe pif-list

Use the pif-param-list command to verify the IP addressing configuration for the PIF that will be used for the management interface. If necessary, use the pif-reconfigure-ip command to configure IP addressing for the PIF to be used. See Chapter 8, Command line interface for more detail on the options available for the pif-reconfigure-ip command.
```
xe pif-param-list uuid=<pif_uuid>
```
Use the host-management-reconfigure CLI command to change the PIF used for the management interface. If this host is part of a resource pool, this command must be issued on the member host console:
```
xe host-management-reconfigure pif-uuid=<pif_uuid>
```

Warning

Putting the management interface on a VLAN network is not supported.

Use the pif-list command to verify that NIC ordering is consistent across your XenServer hosts. Review the MAC address and carrier (link state) parameters associated with each PIF to verify that the devices discovered (eth0, eth1, etc.) correspond to the appropriate physical port on the server.

xe pif-list params=uuid,device,MAC,currently-attached,carrier,management, \
IP-configuration-mode

uuid ( RO)                     : 1ef8209d-5db5-cf69-3fe6-0e8d24f8f518
                   device ( RO): eth0
                      MAC ( RO): 00:19:bb:2d:7e:8a
       currently-attached ( RO): true
               management ( RO): true
    IP-configuration-mode ( RO): DHCP
                  carrier ( RO): true


uuid ( RO)                     : 829fd476-2bbb-67bb-139f-d607c09e9110
                   device ( RO): eth1
                      MAC ( RO): 00:19:bb:2d:7e:7a
       currently-attached ( RO): false
               management ( RO): false
    IP-configuration-mode ( RO): None
                  carrier ( RO): true

If the hosts have already been joined in a pool, add the host-uuid parameter to the pif-list command to scope the results to the PIFs on a given host.

4.2.9.2. Re-ordering NICs

It is not possible to directly rename a PIF, although you can use the pif-forget and pif-introduce commands to achieve the same effect with the following restrictions:

The XenServer host must be standalone and not joined to a resource pool.
Re-ordering a PIF configured as the management interface of the host requires additional steps which are included in the example below. Because the management interface must first be disabled the commands must be entered directly on the host console.

For the example configuration shown above use the following steps to change the NIC ordering so that eth0 corresponds to the device with a MAC address of 00:19:bb:2d:7e:7a:

Use XenCenter or the vm-shutdown command to shut down all VMs in the pool to force existing VIFs to be unplugged from their networks.

xe vm-shutdown uuid=<vm_uuid>

Use the host-management-disable command to disable the management interface:

xe host-management-disable

Use the pif-forget command to remove the two incorrect PIF records:

xe pif-forget uuid=1ef8209d-5db5-cf69-3fe6-0e8d24f8f518
xe pif-forget uuid=829fd476-2bbb-67bb-139f-d607c09e9110

Use the pif-introduce command to re-introduce the devices with the desired naming:

xe pif-introduce device=eth0 host-uuid=<host_uuid> mac=00:19:bb:2d:7e:7a
xe pif-introduce device=eth1 host-uuid=<host_uuid> mac=00:19:bb:2d:7e:8a

Use the pif-list command again to verify the new configuration:

xe pif-list params=uuid,device,MAC

Use the pif-reconfigure-ip command to reset the management interface IP addressing configuration. See Chapter 8, Command line interface for details on the parameters of the pif-reconfigure-ip command.
```
xe pif-reconfigure-ip uuid=<728d9e7f-62ed-a477-2c71-3974d75972eb> mode=dhcp
```
Use the host-management-reconfigure command to set the management interface to the desired PIF and re-enable external management connectivity to the host:
```
xe host-management-reconfigure pif-uuid=<728d9e7f-62ed-a477-2c71-3974d75972eb>
```

4.3. Networking Troubleshooting

If you are having problems with configuring networking, first ensure that you have not directly modified any of the control domain ifcfg-* files directly. These files are directly managed by the control domain host agent, and changes will be overwritten.

4.3.1. Diagnosing network corruption

Some models of network cards require firmware upgrades from the vendor to work reliably under load, or when certain optimizations are turned on. If you are seeing corrupted traffic to VMs, then you should first try to obtain the latest recommended firmware from your vendor and apply a BIOS update.

If the problem still persists, then you can use the CLI to disable receive / transmit offload optimizations on the physical interface.

Warning

Disabling receive / transmit offload optimizations can result in a performance loss and / or increased CPU usage.

First, determine the UUID of the physical interface. You can filter on the device field as follows:

xe pif-list device=eth0

Next, set the following parameter on the PIF to disable TX offload:

xe pif-param-set uuid=<pif_uuid> other-config:ethtool-tx=off

Finally, re-plug the PIF or reboot the host for the change to take effect.

4.3.2. Recovering from a bad network configuration

In some cases it is possible to render networking unusable by creating an incorrect configuration. This is particularly true when attempting to make network configuration changes on a member XenServer host.

If a loss of networking occurs, the following notes may be useful in recovering and regaining network connectivity:

Citrix recommends that you ensure networking configuration is set up correctly before creating a resource pool, as it is usually easier to recover from a bad configuration in a non-pooled state.
The host-management-reconfigure and host-management-disable commands affect the XenServer host on which they are run and so are not suitable for use on one host in a pool to change the configuration of another. Run these commands directly on the console of the XenServer host to be affected, or use the xe -s, -u, and -pw remote connection options.
When the xapi service starts, it will apply configuration to the management interface first. The name of the management interface is saved in the /etc/xensource-inventory file. In extreme cases, you can stop the xapi service by running service xapi stop at the console, edit the inventory file to set the management interface to a safe default, and then ensure that the ifcfg files in /etc/sysconfig/network-scripts have correct configurations for a minimal network configuration (including one interface and one bridge; for example, eth0 on the xenbr0 bridge).

Chapter 5. Workload Balancing

Table of Contents

5.1. Workload Balancing Overview

5.1.1. Workload Balancing Basic Concepts

5.2. Designing Your Workload Balancing Deployment

5.2.1. Deploying One Server
5.2.2. Planning for Future Growth
5.2.3. Increasing Availability
5.2.4. Multiple Server Deployments
5.2.5. Workload Balancing Security

5.3. Workload Balancing Installation Overview

5.3.1. Workload Balancing System Requirements
5.3.2. Workload Balancing Data Store Requirements
5.3.3. Operating System Language Support
5.3.4. Preinstallation Considerations
5.3.5. Installing Workload Balancing

5.4. Windows Installer Commands for Workload Balancing

5.4.1. ADDLOCAL
5.4.2. CERT_CHOICE
5.4.3. CERTNAMEPICKED
5.4.4. DATABASESERVER
5.4.5. DBNAME
5.4.6. DBUSERNAME
5.4.7. DBPASSWORD
5.4.8. EXPORTCERT
5.4.9. EXPORTCERT_FQFN
5.4.10. HTTPS_PORT
5.4.11. INSTALLDIR
5.4.12. PREREQUISITES_PASSED
5.4.13. RECOVERYMODEL
5.4.14. USERORGROUPACCOUNT
5.4.15. WEBSERVICE_USER_CB
5.4.16. WINDOWS_AUTH

5.5. Initializing and Configuring Workload Balancing

5.5.1. Initialization Overview
5.5.2. To initialize Workload Balancing
5.5.3. To edit the Workload Balancing configuration for a pool
5.5.4. Authorization for Workload Balancing
5.5.5. Configuring Antivirus Software
5.5.6. Changing the Placement Strategy
5.5.7. Changing the Performance Thresholds and Metric Weighting

5.6. Accepting Optimization Recommendations

5.6.1. To accept an optimization recommendation

5.7. Choosing an Optimal Server for VM Initial Placement, Migrate, and Resume

5.7.1. To start a virtual machine on the optimal server

5.8. Entering Maintenance Mode with Workload Balancing Enabled

5.8.1. To enter maintenance mode with Workload Balancing enabled

5.9. Working with Workload Balancing Reports

5.9.1. Introduction
5.9.2. Types of Workload Balancing Reports
5.9.3. Using Workload Balancing Reports for Tasks
5.9.4. Creating Workload Balancing Reports
5.9.5. Generating Workload Balancing Reports
5.9.6. Workload Balancing Report Glossary

5.10. Administering Workload Balancing

5.10.1. Disabling Workload Balancing on a Resource Pool
5.10.2. Reconfiguring a Resource Pool to Use Another WLB Server
5.10.3. Uninstalling Workload Balancing

5.11. Troubleshooting Workload Balancing

5.11.1. General Troubleshooting Tips
5.11.2. Error Messages
5.11.3. Issues Installing Workload Balancing
5.11.4. Issues Initializing Workload Balancing
5.11.5. Issues Starting Workload Balancing
5.11.6. Workload Balancing Connection Errors
5.11.7. Issues Changing Workload Balancing Servers

5.1. Workload Balancing Overview

Workload Balancing is a XenServer feature that helps you balance virtual machine workloads across hosts and locate VMs on the best possible servers for their workload in a resource pool. When Workload Balancing places a virtual machine, it determines the best host on which to start a virtual machine or it rebalances the workload across hosts in a pool. For example, Workload Balancing lets you determine where to:

Start a virtual machine
Resume a virtual machine that you powered off
Move virtual machines when a host fails

When Workload Balancing is enabled, if you put a host into Maintenance Mode, Workload Balancing selects the optimal server for each of the host's virtual machines. For virtual machines taken offline, Workload Balancing provides recommendations to help you restart virtual machines on the optimal server in the pool.

Workload Balancing also lets you balance virtual-machine workloads across hosts in a XenServer resource pool. When the workload on a host exceeds the level you set as acceptable (the threshold), Workload Balancing will make recommendations to move part of its workload (for example, one or two virtual machines) to a less-taxed host in the same pool. It does this by evaluating the existing workloads on hosts against resource performance on other hosts.

You can also use Workload Balancing to help determine if you can power off hosts at certain times of day.

Workload Balancing performs these tasks by analyzing XenServer resource-pool metrics and recommending optimizations. You decide if you want these recommendations geared towards resource performance or hardware density. You can fine-tune the weighting of individual resource metrics (CPU, network, memory, and disk) so that the placement recommendations and critical thresholds align with your environment's needs.

To help you perform capacity planning, Workload Balancing provides historical reports about host and pool health, optimization and virtual-machine performance, and virtual-machine motion history.

5.1.1. Workload Balancing Basic Concepts

Workload Balancing captures data for resource performance on virtual machines and physical hosts. It uses this data, combined with the preferences you set, to provide optimization and placement recommendations. Workload Balancing stores performance data in a SQL Server database: the longer Workload Balancing runs the more precise its recommendations become.

Workload Balancing recommends moving virtual-machine workloads across a pool to get the maximum efficiency, which means either performance or density depending on your goals. Within a Workload Balancing context:

Performance refers to the usage of physical resources on a host (for example, the CPU, memory, network, and disk utilization on a host). When you set Workload Balancing to maximize performance, it recommends placing virtual machines to ensure the maximum amount of resources are available for each virtual machine.
Density refers to the number of virtual machines on a host. When you set Workload Balancing to maximize density, it recommends placing virtual machines to ensure they have adequate computing power so you can reduce the number of hosts powered on in a pool.

Workload Balancing configuration preferences include settings for placement (performance or density), virtual CPUs, and performance thresholds.

Workload Balancing does not conflict with settings you already specified for High Availability. Citrix designed the features to work in conjunction with each other.

5.1.1.1. Workload Balancing Component Overview

The Workload Balancing software is a collection of services and components that let you manage all of Workload Balancing's basic functions, such as manage workload and displaying reports. You can install the Workload Balancing services on one computer (physical or virtual) or multiple computers. A Workload Balancing server can manage more than one resource pool.

Workload Balancing consists of the following components:

Workload Balancing server. Collects data from the virtual machines and their hosts and writes the data to the data store. This service is also referred to as the "data collector."
Data Store. A Microsoft SQL Server or SQL Server Express database that stores performance and configuration data.

For more information about Workload Balancing components for large deployments with multiple servers, see Multiple Server Deployments.

5.2. Designing Your Workload Balancing Deployment

You can install Workload Balancing on one computer (physical or virtual) or distribute the components across multiple computers. The three most common deployment configurations are the following:

All components are installed on a single server
The data collector is installed on a dedicated server
All components are installed on a single server, but the data store is installed on central database server

Because one data collector can monitor multiple resource pools, you do not need multiple data collectors to monitor multiple pools.

5.2.1. Deploying One Server

Depending on your environment and goals, you can install Workload Balancing and the data store on one server. In this configuration, one data collector monitors all the resource pools.

The following table shows the advantages and disadvantages to a single-server deployment:

Advantages	Disadvantages
Simple installation and configuration. No Windows domain requirement.	Single point of failure.

5.2.2. Planning for Future Growth

If you anticipate that you will want to add more resource pools in the future, consider designing your Workload Balancing deployment so that it supports growth and scalability. Consider:

Using SQL Server for the data store. In large environments, consider using SQL Server for the data store instead of SQL Server Express. Because SQL Server Express has a 4GB disk-space limit, Workload Balancing limits the data store to 3.5GB when installed on this database. SQL Server has no preset disk-space limitation.
Deploying the data store on a dedicated server. If you deploy SQL Server on a dedicated server (instead of collocating it on the same computer as the other Workload Balancing services), you can let it use more memory.

5.2.3. Increasing Availability

If Workload Balancing's recommendations or reports are critical in your environment, consider implementing strategies to ensure high availability, such as one of the following:

Installing multiple data collectors, so there is not a single point of failure.
Configuring Microsoft clustering. This is the only true failover configuration for single-server deployments. However, Workload Balancing services are not "cluster aware," so if the primary server in the cluster fails, any pending requests are lost when the secondary server in the cluster takes over.
Making Workload Balancing part of a XenServer resource pool with High Availability enabled.

5.2.4. Multiple Server Deployments

In some situations, you might need to deploy Workload Balancing on multiple servers. When you deploy Workload Balancing on multiple servers, you place its key services on one more servers:

Data Collection Manager service. Collects data from the virtual machines and their hosts and writes the data to the data store. This service is also referred to as the "data collector."
Web Service Host. Facilitates communications between the XenServer and the Analysis Engine. Requires a security certificate, which you can create or provide during Setup.
Analysis Engine service. Monitors resource pools and determines if a resource pool needs optimizations.

The size of your XenServer environment affects your Workload Balancing design. Since every environment is different, the size definitions that follow are examples of environments of that size:

Size	Example
Small	One resource pool with 2 hosts and 8 virtual machines
Medium	Two resource pools with 6 hosts and 8 virtual machines per pool
Large	Five resource pools with 16 hosts and 64 virtual machines per pool

5.2.4.1. Deploying Multiple Servers

Having multiple servers for Workload Balancing's services may be necessary in large environments. For example, having multiple servers may reduce "bottlenecks." If you decide to deploy Workload Balancing's services on multiple computers, all servers must be members of mutually trusted Active Directory domains.

Advantages	Disadvantages
Provides better scalability. Can monitor more resource pools.	More equipment to manage and, consequently, more expense.

5.2.4.2. Deploying Multiple Data Collectors

Workload Balancing supports multiple data collectors, which might be beneficial in environments with many resource pools. When you deploy multiple data collectors, the data collectors work together to ensure all XenServer pools are being monitored at all times.

All data collectors collect data from their own resource pools. One data collector, referred to as the master, also does the following:

Checks for configuration changes and determines the relationships between resource pools and data collectors
Checks for new XenServer resource pools to monitor and assigns these pools to a data collector
Monitors the health of the other data collectors

If a data collector goes offline or you add a new resource pool, the master data collector rebalances the workload across the data collectors. If the master data collector goes offline, another data collector assumes the role of the master.

5.2.4.3. Considering Large Environments

In large environments, consider the following:

When you install Workload Balancing on SQL Server Express, Workload Balancing limits the size of the metrics data to 3.5GB. If the data grows beyond this size, Workload Balancing starts grooming the data, deleting older data, automatically.
Citrix recommends putting the data store on one computer and the Workload Balancing services on another computer.
For Workload Balancing data-store operations, memory utilization is the largest consideration.

5.2.5. Workload Balancing Security

Citrix designed Workload Balancing to operate in a variety of environments, and Citrix recommends properly securing the installation. The steps required vary according to your planned deployment and your organization's security policies. This topic provides information about the available options and makes recommendations.

Important

Citrix does not recommend changing the privileges or accounts under which the Workload Balancing services run.

5.2.5.1. Encryption Requirements

XenServer communicates with Workload Balancing using HTTPS. Consequently, you must create or install an SSL/TLS certificate when you install Workload Balancing (or the Web Services Host, if it is on a separate server). You can either use a certificate from a Trusted Authority or create a self-signed certificate using Workload Balancing Setup.

The self-signed certificate Workload Balancing Setup creates is not from a Trusted Authority. If you do not want to use this self-signed certificate, prepare a certificate before you begin Setup and specify that certificate when prompted.

If desired, during Workload Balancing Setup, you can export the certificate so that you can import it into XenServer after Setup.

Note

If you create a self-signed certificate during Workload Balancing Setup, Citrix recommends that you eventually replace this certificate with one from a Trusted Authority.

5.2.5.2. Domain Considerations

When deploying Workload Balancing, your environment determines your domain and security requirements.

If your Workload Balancing services are on multiple computers, the computers must be part of a domain.
If your Workload Balancing components are in separate domains, you must configure trust relationships between those domains.

5.2.5.3. SQL Server Authentication Requirements

When you install SQL Server or SQL Server Express, you must configure Windows authentication (also known as Integrated Windows Authentication). Workload Balancing does not support SQL Server Authentication.

5.3. Workload Balancing Installation Overview

Workload Balancing is a XenServer feature that helps manage virtual-machine workloads within a XenServer environment. Workload Balancing requires that you:

Install SQL Server or SQL Server Express.
Install Workload Balancing on one or more computers (physical or virtual). See Section 5.2, “Designing Your Workload Balancing Deployment”.

Typically, you install and configure Workload Balancing after you have created one or more XenServer resource pools in your environment.

You install all Workload Balancing functions, such as the Workload Balancing data store, the Analysis Engine, and the Web Service Host, from Setup.

You can install Workload Balancing in one of two ways:

Installation Wizard. Start the installation wizard from Setup.exe. Citrix suggests installing Workload Balancing from the installation wizard because this method checks your system meets the installation requirements.
Command Line. If you install Workload Balancing from the command line, the prerequisites are not checked. For Msiexec properties, see Section 5.4, “Windows Installer Commands for Workload Balancing”.

When you install the Workload Balancing data store, Setup creates the database. You do not need to run Workload Balancing Setup locally on the database server: Setup supports installing the data store across a network.

If you are installing Workload Balancing services as components on separate computers, you must install the database component before the Workload Balancing services.

After installation, you must configure Workload Balancing before you can use it to optimize workloads. For information, see Section 5.5, “Initializing and Configuring Workload Balancing”.

For information about System Requirements, see Section 5.3.1, “Workload Balancing System Requirements”. For installation instructions, see Section 5.3.5, “Installing Workload Balancing”.

5.3.1. Workload Balancing System Requirements

This topic provides system requirements for:

For information about data store requirements, see Section 5.3.2, “Workload Balancing Data Store Requirements”.

5.3.1.1. Supported XenServer Versions

XenServer 5.5

5.3.1.2. Supported Operating Systems

Unless otherwise noted, Workload Balancing components run on the following operating systems (32-bit and 64-bit):

Windows Server 2008
Windows Server 2003, Service Pack 2
Windows Vista
Windows XP Professional, Service Pack 2 or Service Pack 3

If you are installing with the User Account Control (UAC) enabled, see Microsoft's documentation.

5.3.1.3. Recommended Hardware

Unless otherwise noted, Workload Balancing components require the following hardware (32-bit and 64-bit):

CPU: 2GHz or faster
Memory: 2GB recommended (1GB of RAM required)
Disk Space: 20GB (minimum)

When all Workload Balancing services are installed on the same server, Citrix recommends that the server have a minimum of a dual-core processor.

5.3.1.4. Data Collection Manager

Operating System Components	Microsoft .NET Framework 3.5, Service Pack 1 or higher
Hard Drive	1GB

5.3.1.5. Analysis Engine

Operating System Components

Microsoft .NET Framework 3.5, Service Pack 1 or higher

5.3.1.6. Web Service Host

Operating System Components

Microsoft .NET Framework 3.5, Service Pack 1 or higher

Operating System	One of the following, as required by your SQL Server edition: Windows Server 2008 Windows Server 2003, Service Pack 1 or higher Windows Vista and Windows XP Professional (for SQL Server Express)
Database	The 32-bit or 64-bit edition of: SQL Server 2008 Express. The 32-bit edition is available on the Workload Balancing installation media in the sql folder. SQL Server 2008 (Standard edition or better) SQL Server 2005, Service Pack 1 or higher (Standard edition or better) Note Windows Server 2008 servers require SQL Server 2005, Service Pack 2 or higher.
Required Configurations	Configure SQL Server for case-insensitive collation. Workload Balancing does not currently support case-sensitive collation. Microsoft SQL Server 2005 Backward Compatibility Components. See Section 5.3.2.3, “Backwards Compatibility Requirement for SQL Server 2008” for more information.
Hard Drive	SQL Server Express: 5GB SQL Server: 20GB

5.3.2.2. SQL Server Database Authentication Requirements

During installation, Setup must connect and authenticate to the database server to create the data store. Configure the SQL Server database instance to use either:

Windows Authentication mode, or
SQL Server and Windows Authentication mode (Mixed Mode authentication)

If you create an account on the database for use during Setup, the account must have sysadmin privileges for the database instance where you want to create the Workload Balancing data store.

5.3.2.3. Backwards Compatibility Requirement for SQL Server 2008

After installing SQL Server Express 2008 or SQL Server 2008, you must install the SQL Server 2005 Backward Compatibility Components on all Workload Balancing computers before running Workload Balancing Setup. The Backward Compatibility components let Workload Balancing Setup configure the database.

The Workload Balancing installation media includes the 32-bit editions of SQL Server Express 2008 and the SQL Server 2005 Backward Compatibility Components.

While some SQL Server editions may include the Backward Compatibility components with their installation programs, their Setup program might not install them by default.
You can also obtain the Backward Compatibility components from the download page for the latest Microsoft SQL Server 2008 Feature Pack.

Install the files in the sql folder in the following order:

en_sql_server_2008_express_with_tools_x86.exe. Installs SQL Server Express, 32-bit edition. Requires installing Microsoft .NET Framework 3.5, Service Pack 1 first.
SQLServer2005_BC.msi. Installs the SQL Server 2005 Backward Compatibility Components for 32-bit computers.

5.3.3. Operating System Language Support

Workload Balancing is supported on the following operating system languages:

US English
Japanese (Native JP)

Note

In configurations where the database and Web server are installed on separate servers, the operating system languages must match on both computers.

5.3.4. Preinstallation Considerations

You may need to configure software in your environment so that Workload Balancing can function correctly. Review the following considerations and determine if they apply to your environment. Also, check the XenServer readme for additional, late-breaking release-specific requirements.

Account for Workload Balancing. Before Setup, you must create a user account for XenServer to use to connect to Workload Balancing (specifically the Web Service Host service). This user account can be either a domain account or an account local to the computer running Workload Balancing (or the Web Service Host service).
Important
When you create this account in Windows, Citrix suggests enabling the Password never expires option.
During Setup, you must specify the authorization type (a single user or group) and the user or group with permissions to make requests of the Web Service Host service. For additional information, see Section 5.5.4, “Authorization for Workload Balancing ”.
SSL/TLS Certificate. XenServer and Workload Balancing communicate over HTTPS. Consequently, during Workload Balancing Setup, you must provide either an SSL/TLS certificate from a Trusted Authority or create a self-signed certificate.
Group Policy. If the server on which you are installing Workload Balancing is a member of a Group Policy Organizational Unit, ensure that current or scheduled, future policies do not prohibit Workload Balancing or its services from running.

Note

In addition, review the applicable release notes for release-specific configuration information.

5.3.5. Installing Workload Balancing

Before installing Workload Balancing, you must:

Install a SQL Server or SQL Server Express database as described in Workload Balancing Data Store Requirements.
Have a login on the SQL Server database instance that has SQL Login creation privileges. For SQL Server Authentication, the account needs sysadmin privileges.
Create an account for Workload Balancing, as described in Preinstallation Considerations and have its name on hand.
Configure all Workload Balancing servers to meet the system requirements described in Workload Balancing System Requirements.

After Setup is finished installing Workload Balancing, verify that it configure Workload Balancing before it begins gathering data and making recommendations.

5.3.5.1. To install Workload Balancing on a single server

The following procedure installs Workload Balancing and all of its services on one computer:

Launch the Workload Balancing Setup wizard from Autorun.exe, and select the Workload Balancing installation option.
After the initial Welcome page appears, click Next.
In the Setup Type page, select Workload Balancing Services and Data Store, and click Next. This option lets you install Workload Balancing, including the Web Services Host, Analysis Engine, and Data Collection Manager services. After you click Next, Workload Balancing Setup verifies that your system has the correct prerequisites.
Accept the End-User License Agreement.
In the Component Selection page, select all of the following components:
In the Database Server page, in the SQL Server Selection section, select one of the following:
- Enter the name of a database server . Lets you type the name of the database server that will host the data store. Use this option to specify an instance name.
  Note
  If you installed SQL Express and specified an instance name, append the server name with \yourinstancename. If you installed SQL Express without specifying an instance name, append the server name with \sqlexpress.
- Choose an existing database server . Lets you select the database server from a list of servers Workload Balancing Setup detected on your network. Use the first option (Enter the name of a database) if you specified an instance name.
In the Install Using section, select one of the following methods of authentication:
- Windows Authentication . This option uses your current credentials (that is, the Windows credentials you used to log on to the computer on which you are installing Workload Balancing). To select this option, your current Windows credentials must have been added as a login to the SQL Server database server (instance).
- SQL Server Authentication . To select this option, you must have configured SQL Server to support Mixed Mode authentication.
  Note
  Citrix recommends clicking Test Connect to ensure Setup can use the credentials you provided to contact the database server.
In the Database Information page, select Install a new Workload Balancing data store and type the name you want to assign to the Workload Balancing database in SQL Server. The default database name is WorkloadBalancing.
In the Web Service Host Account Information page, select HTTPS end point (selected by default). Edit the port number, if necessary; the port is set to 8012 by default.
Note
If you are using Workload Balancing with XenServer, you must select HTTPS end points. XenServer can only communicate with the Workload Balancing feature over SSL/TLS. If you change the port here, you must also change it on XenServer using either the Configure Workload Balancing wizard or the XE commands.
For the account (on the Workload Balancing server) that XenServer will use to connect to Workload Balancing, select the authorization type, User or Group, and type one of the following :
- User name. Enter the name of the account you created for XenServer (for example, workloadbalancing_user).
- Group name. Enter the group name for the account you created. Specifying a group name lets you specify a group of users that have been granted permission to connect to the Web Service Host on the Workload Balancing server. Specifying a group name lets more than one person in your organization log on to Workload Balancing with their own credentials. (Otherwise, you will need to provide all users with the same set of credentials to use for Workload Balancing.)
Specifying the authorization type lets Workload Balancing recognize the XenServer's connection. For more information, see Section 5.5.4, “Authorization for Workload Balancing ”. You do not specify the password until you configure Workload Balancing.
In the SSL/TLS Certificate page, select one of the following certificate options:
Click Install.

5.3.5.2. To install the data store separately

The following procedure installs the Workload Balancing data store only:

From any server with network access to the database, launch the Workload Balancing Setup wizard from Autorun.exe, and select the WorkloadBalancing installation option.
After the initial Welcome page appears, click Next.
In the Setup Type page, select Workload Balancing Database Only, and click Next.This option lets you install the Workload Balancing data store only. After you click Next, Workload Balancing Setup verifies that your system has the correct prerequisites.
Accept the End-User License Agreement, and click Next.
In the Component Selection page, accept the default installation and click Next. This option creates and configures a database for the Workload Balancing data store.
In the Database Server page, in the SQL Server Selection section, select one of the following:
- Enter the name of a database server. Lets you type the name of the database server that will host the data store. Use this option to specify an instance name.
  Note
  If you installed SQL Express and specified an instance name, append the server name with \yourinstancename. If you installed SQL Express without specifying an instance name, append the server name with \sqlexpress.
- Choose an existing database server. Lets you select the database server from a list of servers Workload Balancing Setup detected on your network.
In the Install Using section, select one of the following methods of authentication:
- Windows Authentication. This option uses your current credentials (that is, the Windows credentials you used to log on to the computer on which you are installing Workload Balancing). To select this option, your current Windows credentials must have been added as a login to the SQL Server database server (instance).
- SQL Server Authentication. To select this option, you must have configured SQL Server to support Mixed Mode authentication.
  Note
  Citrix recommends clicking Test Connect to ensure Setup can use the credentials you provided to contact the database server.
In the Database Information page, select Install a new Workload Balancing data store and type the name you want to assign to the Workload Balancing database in SQL Server. The default database name is WorkloadBalancing.
Click Install to install the data store.

5.3.5.3. To install Workload Balancing components separately

The following procedure installs Workload Balancing services on separate computers:

Launch the Workload Balancing Setup wizard from Autorun.exe, and select the WorkloadBalancing installation option.
After the initial Welcome page appears, click Next.
In the Setup Type page, select Workload Balancing Server Services and Database.This option lets you install Workload Balancing, including the Web Services Host, Analysis Engine, and Data Collection Manager services.Workload Balancing Setup verifies that your system has the correct prerequisites.
Accept the End-User License Agreement, and click Next.
In the Component Selection page, select the services you want to install:
In the Database Server page, in the SQL Server Selection section, select one of the following:
- Enter the name of a database server. Lets you type the name of the database server that is hosting the data store.
  Note
  If you installed SQL Express and specified an instance name, append the server name with \yourinstancename. If you installed SQL Express without specifying an instance name, append the server name with \sqlexpress.
- Choose an existing database server. Lets you select the database server from a list of servers Workload Balancing Setup detected on your network.
Note
Citrix recommends clicking Test Connect to ensure Setup can use the credentials you provided to contact the database server successfully.
In the Web Service Information page, select HTTPS end point (selected by default) and edit the port number, if necessary. The port is set to 8012 by default.
Note
If you are using Workload Balancing with XenServer, you must select HTTPS end points. XenServer can only communicate with the Workload Balancing feature over SSL/TLS. If you change the port here, you must also change it on XenServer using either the Configure Workload Balancing wizard or the XE commands.
For the account (on the Workload Balancing server) that XenServer will use to connect to Workload Balancing, select the authorization type, User or Group, and type one of the following:
In the SSL/TLS Certificate page, select one of the following certificate options:
Click Install.

5.3.5.3.1. To verify your Workload Balancing installation

Workload Balancing Setup does not install an icon in the Windows Start menu. Use this procedure to verify that Workload Balancing installed correctly before trying to connect to Workload Balancing with the Workload Balancing Configuration wizard.

Verify Windows Add or Remove Programs (Windows XP) lists Citrix Workload Balancing in its in the list of currently installed programs.
Check for the following services in the Windows Services panel:
All of these services must be started and running before you start configuring Workload Balancing.
If Workload Balancing appears to be missing, check the installation log to see if it installed successfully:
- If you used the Setup wizard, the log is at %Documents and Settings%\username\Local Settings\Temp\msibootstrapper2CSM_MSI_Install.log (by default). On Windows Vista and Windows Server 2008, this log is at %Users%\username\AppData\Local\Temp\msibootstrapper2CSM_MSI_Install.log. User name is the name of the user logged on during installation.
- If you used the Setup properties (Msiexec), the log is at C:\log.txt (by default) or wherever you specified for Setup to create it.

5.4. Windows Installer Commands for Workload Balancing

The Workload Balancing installation supports using the Msiexec command for Setup. The Msiexec command lets you install, modify, and perform operations on Windows Installer (.msi) packages from the command line.

Set properties by adding Property=”value” on the command line after other switches and parameters.

The following sample command line performs a full installation of the Workload Balancing Windows Installer package and creates a log file to capture information about this operation.

msiexec.exe /I C:\path-to-msi\workloadbalancingx64.msi /quiet 
PREREQUISITES_PASSED="1" 
DBNAME="WorkloadBalancing1" 
DATABASESERVER="WLB-DB-SERVER\INSTANCENAME" 
HTTPS_PORT="8012" 
WEBSERVICE_USER_CB="0" 
USERORGROUPACCOUNT="domain\WLBgroup" 
CERT_CHOICE="0" 
CERTNAMEPICKED="cn=wlb-cert1" 
EXPORTCERT=1
EXPORTCERT_FQFN="C:\Certificates\WLBCert.cer"
INSTALLDIR="C:\Program Files\Citrix\WLB" 
ADDLOCAL="Database,Complete,Services,DataCollection,
Analysis_Engine,DWM_Web_Service" /l*v log.txt

There are two Workload Balancing Windows Installer packages: workloadbalancing.msi and workloadbalancingx64.msi. If you are installing Workload Balancing on a 64-bit operating system, specify workloadbalancingx64.msi.

To see if Workload Balancing Setup succeeded, see Section 5.3.5.3.1, “To verify your Workload Balancing installation”.

Separate entries by commas.
The values must be installed locally.
You must install the data store on a shared or dedicated server before installing other services.
You can only install services standalone, without installing the database simultaneously, if you have a Workload Balancing data store installed and specify it in the installation script using and for the database type. See Section 5.4.5, “DBNAME” and Section 5.4.4, “DATABASESERVER” for more information.

Required property for all installations.
Whether installing a database or connecting to an existing data store, you must specify this property with DBNAME.
Even if you are specifying a database on the same computer as you are performing Setup, you still must define the name of the database.
When you specify DATABASESERVER, in some circumstances, you must specify also Section 5.4.16, “WINDOWS_AUTH” and its accompanying properties.

Required property for all installations. You must set a value for this property.
Whether connecting to or installing a data store, you must specify this property with DATABASESERVER.
Even if you are specifying a database on the same computer as you are performing Setup, you still must define the name of the database.
Localhost is not a valid value.

This property is used with WINDOWS_AUTH (see Section 5.4.16, “WINDOWS_AUTH”) and DBPASSWORD (see Section 5.4.7, “DBPASSWORD”.)
Because you specify the server name and instance using Section 5.4.4, “DATABASESERVER”, do not qualify the user name.

Use this property with the parameters documented in Section 5.4.16, “WINDOWS_AUTH” and Section 5.4.6, “DBUSERNAME”.

0. Does not exports the certificate.
1. Exports the certificate and saves it to the location of your choice with the file name you specify using EXPORTCERT_FQFN.

5.4.8.3. Default value

5.4.8.4. Remarks

Use with Section 5.4.9, “EXPORTCERT_FQFN”, which specifies the file name and path.
Setup does not require this property to run successfully. (That is, you do not have to export the certificate.)
This property lets you export self-signed certificates that you create during Setup as well as certificates that you created using a Trusted Authority.

If you set a value other than the default for this property, you must also change the value of this port in XenServer, which you can do with the Configure Workload Balancing wizard. The port number value specified during Setup and in the Configure Workload Balancing wizard must match.

You must set this property for Setup to continue. When enabled (PREREQUISITES_PASSED = 1), Setup skips checking preinstallation requirements, such as memory or operating system configurations, and lets you perform a command-line installation of the server.

5.4.12.2. Possible values

1. Indicates for Setup to not check for preinstallation requirements on the computer on which you are running Setup. You must set this property to 1 or Setup fails.

5.4.12.3. Default value

5.4.12.4. Remarks

This is a required value.

SIMPLE. Specifies the SQL Server Simple Recovery model. Lets you recover the database from the end of any backup. Requires the least administration and consumes the lowest amount of disk space.
FULL. Specifies the Full Recovery model. Lets you recover the database from any point in time. However, this model uses consumes the largest amount of disk space for its logs.
BULK_LOGGED. Specifies the Bulk-Logged Recovery model. Lets you recover the database from the end of any backup. This model consumes less logging space than the Full Recovery model. However, this model provides more protection for data than the Simple Recovery model.

User name. Specify the name of the account you created for XenServer (for example, workloadbalancing_user).
Group name. Specify the group name for the account you created. Specifying a group name lets more than one person in your organization log on to Workload Balancing with their own credentials. (Otherwise, you will have to provide all users with the same set of credentials to use for Workload Balancing.)

5.4.14.3. Default value

Blank.

5.4.14.4. Remarks

This is a required parameter. You must use this parameter with Section 5.4.15, “WEBSERVICE_USER_CB ”.
To specify this parameter, you must create an account on the Workload Balancing server before running Setup. For more information, see Section 5.5.4, “Authorization for Workload Balancing ”.
This property does not require specifying another property for the password. You do not specify the password until you configure Workload Balancing.

0. SQL Server authentication
1. Windows authentication

5.4.16.3. Default value

5.4.16.4. Remarks

If you are logged into the server on which you are installing Workload Balancing with Windows credentials that have an account on the database server, you do not need to set this property.
If you specify WINDOWS_AUTH, you must also specify DBPASSWORD if you want to specify an account other than the one you are logged onto the server on which you are running Setup.
The account you specify must be a login on the SQL Server database with sysadmin privileges.

5.5. Initializing and Configuring Workload Balancing

Following Workload Balancing Setup, you must configure and enable (that is, initialize) Workload Balancing on each resource pool you want to monitor before Workload Balancing can gather data for that pool.

Before initializing Workload Balancing, configure your antivirus software to exclude Workload Balancing folders, as described in Section 5.5.5, “Configuring Antivirus Software”.

After the initial configuration, the Initialize button on the WLB tab changes to a Disable button. This is because after initialization you cannot modify the Workload Balancing server a resource pool uses without disabling Workload Balancing on that pool and then reconfiguring it. For information, see Section 5.10.2, “Reconfiguring a Resource Pool to Use Another WLB Server”.

Important

Following initial configuration, Citrix strongly recommends you evaluate your performance thresholds as described in Section 5.9.3.1, “Evaluating the Effectiveness of Your Optimization Thresholds”. It is critical to set Workload Balancing to the correct thresholds for your environment or its recommendations might not be appropriate.

You can use the Configure Workload Balancing wizard in XenCenter or the XE commands to initialize Workload Balancing or modify the configuration settings.

5.5.1. Initialization Overview

Initial configuration requires that you:

Specify the Workload Balancing server you want the resource pool to use and its port number.
Specify the credentials for communications, including the credentials:
- XenServer will use to connect to the Workload Balancing server
- Workload Balancing will use to connect to XenServer
For more information, see Section 5.5.4, “Authorization for Workload Balancing ”
Change the optimization mode, if desired, from Maximum Performance, the default setting, to Maximize Density. For information about the placement strategies, see Section 5.5.6, “Changing the Placement Strategy”.
Modify performance thresholds, if desired. You can modify the default utilization values and the critical thresholds for resources. For information about the performance thresholds, see Section 5.5.7, “Changing the Performance Thresholds and Metric Weighting”.
Modify metric weighting, if desired. You can modify the importance Workload Balancing assigns to metrics when it evaluates resource usage. For information about the performance thresholds, see Section 5.5.7.2, “Metric Weighting Factors”.

5.5.2. To initialize Workload Balancing

Use this procedure to enable and perform the initial configuration of Workload Balancing for a resource pool.

Before the Workload Balancing feature can begin collecting performance data, the XenServers you want to balance must be part of a resource pool. To complete this wizard, you need the:

IP address (or NetBIOS name) and (optionally) port of the Workload Balancing server
Credentials for the resource pool you want Workload Balancing to monitor
Credentials for the account you created on the Workload Balancing server

In the Resources pane of XenCenter, select XenCenter > <your-resource-pool>.
In the Properties pane, click the WLB tab.
In the WLB tab, click Initialize WLB.
In the Configure Workload Balancing wizard, click Next.
In the Server Credentials page, enter the following:
In the Basic Configuration page, do the following:

Do one of the following:

If you...	then...
want to modify advanced settings for thresholds and change the priority given to specific resources	click Next and continue with this procedure.
do not want to configure additional settings	click Finish.

In Critical Thresholds page, accept or enter a new value in the Critical Thresholds boxes.Workload Balancing uses these thresholds when making virtual-machine placement and pool-optimization recommendations. Workload Balancing strives to keep resource utilization on a host below the critical values set. For information about adjusting these thresholds, see Critical Thresholds.
In Metric Weighting page, if desired, adjust the sliders beside the individual resources. Moving the slider towards Less Important indicates that ensuring virtual machines always have the highest amount of this resource available is not as vital on this resource pool. For information about adjusting metric weighting, see Metric Weighting Factors.
Click Finish.

5.5.3. To edit the Workload Balancing configuration for a pool

After initialization, you can use this procedure to edit the Workload Balancing performance thresholds and placement strategies for a specific resource pool.

In the Resources pane of XenCenter, select XenCenter > <your-resource-pool> .
In the Properties pane, click the WLB tab.
In the WLB tab, click Configure WLB.
In the Configure Workload Balancing wizard, click Next.
In the Basic Configuration page, do the following:

Do one of the following:

If you...	then...
want to modify advanced settings for thresholds and change the priority given to specific resources	click Next and continue with this procedure.
do not want to configure additional settings	click Finish.