XenCenter

PVS-Accelerator

The Citrix Hypervisor PVS-Accelerator feature offers extra capabilities for customers using Citrix Hypervisor and Citrix Provisioning (PVS). PVS is a popular choice for image management and hosting for Citrix Virtual Apps and Desktops. With this feature, PVS read requests can now be cached on each Citrix Hypervisor host. To benefit from the PVS-Accelerator feature, use Citrix Hypervisor with Citrix Provisioning 7.12 or higher. For detailed information about PVS-Accelerator, see the product documentation.

Enabling the PVS-Accelerator involves a simple three-step process:

  1. Install the PVS-Accelerator Supplemental Pack on the Citrix Hypervisor server.
  2. Configure PVS-Accelerator in Citrix Hypervisor.
  3. Complete the cache configuration in PVS.

Enabling PVS-Accelerator

To enable the PVS-Accelerator feature, complete the following configuration settings in Citrix Hypervisor and in PVS:

  1. Install the PVS-Accelerator Supplemental Pack on each Citrix Hypervisor host in the pool. The supplemental pack is available to download from the Citrix Hypervisor Product Downloads page. For instructions on how to install the supplemental pack, see Installing Supplemental Packs.
  2. Configure PVS-Accelerator in Citrix Hypervisor. This configuration can be done using XenCenter or the xe CLI.

    After installing the PVS-Accelerator Supplemental Pack, add the PVS-Accelerator configuration details in the Citrix Hypervisor server. This process entails adding a PVS site and specifying the PVS Cache storage.

    The following section contains XenCenter instructions. For information about configuring the PVS-Accelerator using the xe CLI, see the Citrix Hypervisor product documentation.

    The PVS tab appears at the pool-level (or host-level if there is no pool) in XenCenter after installing the PVS-Accelerator Supplemental Pack, and assigning a license with entitlement. The PVS tab displays a summary of the Read caching status for all the VMs running inside the pool.

    To configure PVS-Accelerator

    1. Select the pool or the standalone host and then select the PVS tab.
    2. Select Configure PVS-Accelerator.
    3. On the PVS-Accelerator configuration dialog, select Add cache configuration to add a PVS site.
      • Enter a name for the PVS site in the Site name field.
      • For each host in the pool, specify what cache to use:

        • When you select Memory only, the feature uses up to the specified cache size in the Control Domain memory. This option is only available after extra memory has been assigned to the Control Domain. For information on how to assign memory to the Control Domain, see Changing the Control Domain Memory.
        • When you select a Storage Repository (SR), the feature uses up to the specified cache size on the SR. It also implicitly uses available control domain memory as a best effort cache tier.

        Important:

        • If neither Memory only nor an SR is specified, the read cache is not activated.
        • PVS-Accelerator has been designed to utilize either memory only, or a combination of disk and memory. Irrespective of the configuration choice, increase the amount of memory allocated to the Control Domain to ensure there is no system performance degradation.
        • We recommend that you allocate at least 4 GB of Control Domain memory per host to avoid frequent disk accesses that cause higher read-latency and therefore degrade performance. For more information, see Changing the Control Domain Memory.
        • We recommend that you allocate at least 5 GB of cache space per vDisk version that you actively use.
    4. Click OK. The new PVS site and the chosen cache storage configuration are added in the Citrix Hypervisor server.
  3. After configuring the PVS-Accelerator in the Citrix Hypervisor server, complete the cache configuration for the newly created site using the Citrix Provisioning Console or the PowerShell Snap-In CLI. For more information, see Citrix Provisioning Documentation. When this step is complete, you can view a list of PVS Servers configured for the new site by clicking View PVS Servers on the PVS-Accelerator configuration dialog.

Cache operation

After you start a VM with PVS-Accelerator, the caching status for the VM is displayed on the PVS tab and on the General tab of the VM. The following table lists the status messages displayed on these tabs.

PVS-Accelerator status Description
Initialized PVS-Accelerator has been started and is ready to cache. If the cache remains in this state when the VM has been booted, it means that the PVS Server IP addresses have not been configured correctly, or the VM is not communicating with the PVS server using its primary network interface.
Caching PVS-Accelerator is working.
Stopped PVS-Accelerator is not running for the VM. The cache remains in this state when the VM is not running, or when the cache is not configured sufficiently.
Incompatible Write Cache Mode There is no caching as the VM is configured to persist changes on the PVS server. Ensure the VM type is “Production” or “Test” and the vDisk is in “Standard Image” Access mode.
Incompatible Protocol Version The PVS Server version is incorrect. Ensure that you are using Provisioning Services 7.12 or higher.

The PVS-Accelerator functionality caches:

  • Reads from a vDisk but not writes or reads from a write cache
  • Based on image versions. Multiple VMs share cached blocks if they use the same image version
  • Devices with any write cache type
  • A vDisk with the Access mode set to Standard Image. Caching is not compatible with any vDisk set to Private Image mode
  • Devices that are marked as type Production or Test. Devices marked as type Maintenance are not cached

Notes:

  • PVS-Accelerator is available for Citrix Hypervisor Premium Edition customers, or customers who have access to Citrix Hypervisor through their Citrix Virtual Apps and Desktops entitlement.
  • XenCenter displays various PVS-Accelerator performance graphs on the host-level Performance tab. The performance graphs provide detailed insight into the cache operation.
  • The PVS-Accelerator feature uses the capabilities of OVS and is therefore not available on hosts that use Linux Bridge as the network back end.
  • PVS-Accelerator works on the first virtual network interface (VIF) of a cached VM. Therefore, use the first VIF to connect the PVS storage network for the caching to work.

PVS-Accelerator