Citrix Provisioning Accelerator
Citrix Provisoning Accelerator enables a provisioning proxy to reside in Dom0 (the XenServer Control Domain) on a XenServer host where streaming of a provisioning vDisk is cached at the proxy before being forwarded to the VM. Using the cache, subsequent booting (or any IO requests) of the VM on the same host can be streamed from the proxy rather than streaming from the server over the network. Using this model, more local resources on the XenServer host are consumed, but streaming from the server over the network saves resources, effectively improving performance.
With this functionality:
- Citrix Provisioning and XenServer provide an improved functional paradigm by providing a unique value available when used together.
- Citrix Provisioning provides support for local, NAS, and SAN attached storage in XenServer.
- Environments experience reduced network traffic.
- Deployments experience improved fault tolerance, with tolerance for outage instances of a Citrix Provisioning server.
This feature is only supported on XenServer version 7.1 (or later) with the proxy capability installed. UI changes only occur when you are using that type of hypervisor. To use this feature, an optional package must be installed on the XenServer host. There are no additional dependencies on the installer.
For more information on the relationship between XenServer and Citrix Provisioning, refer to the blog XenServer and Citrix Provisioning: Better Together.
Citrix recommends that you do not disable this feature on a VM using the XenServer console. When disabled using this method, Citrix Provisioning fails to recognize the configuration change and continues to believe that the accelerator feature is enabled on that VM. If you want to disable this feature for a single device, see the sections Enabling or disabling Citrix Provisioning Accelerator for individual devices and Enabling or disabling Citrix Provisioning Accelerator for all devices on a host later in this article.
Using Citrix Provisioning Accelerator
The proxy feature is only supported on XenServer with the proxy capability installed (version 7.1). UI changes only occur when you are using that type of hypervisor. An optional package must be installed on the XenServer host. There are no additional dependencies on the installer.
Before using this feature the XenServer administrator must create a Citrix Provisioning Site object using the XenServer console. This process effectively configures the storage (that is, storage repositories) that is used when proxying the IO requests. This work must be performed on XenServer.
Consider the following when using this feature with XenServer:
- A XenServer Citrix Provisioning site object must be created and configured with the storage repository (SR) before the Citrix Provisioning console can establish a proxy connection on the VM.
- Citrix Provisioning calls the XenServer API to check if the proxy feature is enabled before it exposes any provisioning/XenServer proxy interfaces.
- Citrix Provisioning configures the XenServer proxy for devices using the Citrix Virtual Apps and Desktops Setup Wizard and the Streamed VM Setup Wizard.
- Citrix Provisioning targets are aware of their proxy status. Once the feature is installed, no additional configuration tasks are required.
- After reinstalling XenServer, the accelerator cache remains configured in the Citrix Provisioning database. This process causes an error in the VM setup wizard because Citrix Provisioning assumes that the cache still exists. To resolve this issue, delete and then add the XenServer host using the provisioning console. This procedure enables Citrix Provisioning to clear the stored cache configuration. After the stored cache configuration has been cleared, the administrator can create a one in XenCenter.
In environments where two provisioning servers reside with the same VHD but have different file system timestamps, the data is cached twice. Due to this limitation, Citrix recommends that you use VHDX rather than VHD.
Configuring Citrix Provisioning Accelerator
Use the Citrix Virtual Apps and Desktops Setup Wizard and the Streaming Wizard to access this feature. Both Wizards are similar, and share many of the same screens. The following differences exist:
- The Citrix Virtual Apps and Desktops Setup Wizard is used to configure VMs running on a hypervisor (for example, XenServer, Esx, or HyperV/SCVMM) that is controlled using Citrix Virtual Apps and Desktops.
- The Streaming Wizard is used to create VMs on a XenServer host. It does not involve Citrix Virtual Apps and Desktops.
This feature is only supported on XenServer that has the capability installed. UI changes captured in this section only apply when you are using that type of hypervisor.
When a proxy cache configuration (that is, Citrix Provisioning Accelerator is enabled) is tied to a provisioning server, and you reinstall XenServer on the host that had this feature enabled, Citrix Provisioning and XenServer become out of sync. This configuration occurs because the reinstallation of XenServer wipes the previously configured proxy cache configuration.
In this scenario, Citrix Provisioning assumes that the proxy cache configuration still exists, and when the Streamed VM Setup Wizard is used, it fails. This process indicates that the provided UUID (associated with the proxy configuration) is invalid. For this reason, the user must delete all previously configured VMs associated with this cache configuration, including the host. Reconfigure Citrix Provisioning and set up the cache again.
To configure Citrix Provisioning Accelerator, select one of the Wizards (Citrix Virtual Apps and Desktops Setup Wizard or Streamed VM Setup Wizard) in the provisioning console:
- Navigate to a site.
- Select the site, then right-click to expose a contextual menu:
- Select the appropriate Wizard based on how you intend to use the accelerator feature.
Using Wizards to configure Citrix Provisioning Accelerator
To use this feature, first determine how you use it. If you are:
- configuring VMs running on a hypervisor controlled by Citrix Virtual Apps and Desktops, use the Citrix Virtual Apps and Desktops Setup Wizard.
- creating VMs on a XenServer host that does not involve Citrix Virtual Apps and Desktops, use the Streamed VM Setup Wizard.
Configure proxy-accelerator using the streamed VM Setup Wizard
The Streamed Virtual Machine Setup Wizard was modified to include a new checkbox to enable the feature. After invoking the Wizard, select Enable PVS-Accelerator for all Virtual Machines:
After selecting Enable PVS-Accelerator for all Virtual Machines, all VMs that are created using the Wizard are configured to use the proxy feature.
After enabling this feature, the following screen appears (the first time PVS-Accelerator is enabled for the host) after clicking Next:
The Wizard allows you to select the XenServer Citrix Provisioning site to which you want to apply accelerator functionality. In the XenServer screen, a drop-down list displays the list of all the Citrix Provisioning site objects on XenServer that have been configured but not yet associated with a provisioning site.
In the drop-down menu, select a provisioning site to associate with accelerator functionality. After selecting it, the site is now associated with the Citrix Provisioning site that was selected from which to run the Wizard.
The next time this Wizard is run for the same Citrix Provisioning site using the same XenServer, this page is not displayed.
After using one of the Wizards to configure this feature, the Summary screen appears to illustrate the current state. Use this screen to determine if it is enabled, and the current cache configuration associated with it.
Click Finish to apply the configuration:
Enabling or disabling Citrix Provisioning Accelerator for individual devices
If a device was created using either Wizard (Citrix Virtual Apps and Desktops Setup Wizard or the Streaming Wizard), and Citrix Provisioning Accelerator was configured for that XenServer host in the Wizard, you can use the Target Device Properties screen to enable or disable the feature for an individual device.
To enable or disable this feature for an individual device:
Access the Target Device Properties screen.
In the General tab, select (or deselect) PVS-Accelerator Configured.
Click OK to apply the change.
Disabling Citrix Provisioning Accelerator for all devices on a host
If this feature was enabled for a host, you can disable it using the Virtual Host Connection Properties screen for all devices on the specified host.
You cannot use the Virtual Host Connection Properties screen to enable PVS-Accelerator on the specified host. You must enable the feature using one of the Wizards (Citrix Virtual Apps and Desktops Setup Wizard or Streamed Wizard) while creating devices.
To disable this feature for all devices on the specified host:
Access the Virtual Host Connection Properties screen.
In the General tab, select (or deselect)PVS-Accelerator Enabled.
You are prompted to confirm the following action:
After verifying the action, click OK to apply the change.