Product Documentation

To create a virtual hard disk

Dec 17, 2015

For pooled XenDesktop environments, in the profiling wizard, Citrix recommends using the option to Create virtual hard disk (VHD) for this target to improve application launch time. This option is not needed in other deployments, but if enabled, it does not interfere with normal behavior.

Tip: If selected, the profiling workstation and the App Hub need up to twice the amount of disk space available as is normally used for the profile.
In addition to creating the normal directory files, this option creates a virtual hard disk (VHD) while profiling. If selected, the first time users launch the application:
  • In pooled XenDesktop environments, the Offline Plug-in checks the UseVHD registry setting, and if it is set to mount the VHD, the launch copies all profile contents to the VHD in the RadeCache location in the App Hub. Subsequent launches access the files stored on the VHD, which speeds up launch time.
    Note: If you provisioned the pooled XenDesktop through Citrix Provisioning Server or XenDesktop Controller, the Offline Plug-in automatically detects the need to mount the VHD, regardless of this setting.
  • In other environments, the application launches from the directory files in the App Hub, as usual.
This option does not support:
  • Applications streamed using HTTP protocol
  • Offline access to streamed applications

For linked profiles (those enabled for inter-isolation communication), an application launches from a VHD only if the option is enabled for its individual profile. For example, if you profile the first application and select the VHD option, and then link the profile to a second profile without the VHD option, only the first application launches from the VHD; the second application launches from the directory files in the App Hub, as usual.

To unmount the VHD

With administrator privileges, from the command-line, use either of the following commands:
  • radecache /flush:GUID
  • radecache /flushall

To mount the VHD on non-pooled XenDesktop devices

In addition to pooled XenDesktop environments, this option is also beneficial in environments that operate without a physical hard disk, such as XenApp running on virtual servers. If the RadeCache location for the "local" hard disk is across the network to a virtual infrastructure, you can manually set the UseVHD registry to mount the VHD (recommended by Citrix).

On the user device, create the registry key:
  • For 32-bit: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\Rade\UseVHD
  • For 64-bit: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\Rade\UseVHD
Set a DWORD value:
  • 0: Do not mount (default on non-pooled XenDesktop devices).
  • 1: Mount occurs. The VHD attempts to be mounted in the RadeCache folder at the time of sandbox creation.

To configure a fallback method manually

For situations where the VHD fails to mount, you can create a registry key with a fall-back option:
  • For 32-bit: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\Rade\ VHDErrorFallback
  • For 64-bit: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\Rade\VHDErrorFallback
Set a DWORD value:
  • 0: Deny application launch if there is no VHD or mounting the VHD failed because of any other reason.
  • 1: If the VHD is not present, launch the application, but if the VHD cannot be mounted, deny application launch (default behavior, even if registry entry is not created).
  • 2: Launch the application.