Sep. 13, 2016
This topic covers items you should consider when configuring and managing a personal vDisk (PvD) environment. It also covers best practice guidelines and task descriptions.
At restarts, PvD determines the free space remaining in the application area (UserData.v2.vhd). If this falls below 10%, the application area is expanded into any unused profile area space (by default, the space available on the P: drive). The space added to the application area is approximately 50% of the combined free space remaining in both the application area and the profile area.
For example, if the application area on a 10 GB PvD (which by default is 5 GB) reaches 4.7 GB and the profile area has 3 GB free, the increased space that is added to the application area is calculated as follows:
increased space = (5.0-4.7)/2 + 3.0/2 = 1.65 GB
The space added to the application area is only approximate because a small allowance is made for storing logs and for overhead. The calculation and the possible resizing is performed on each restart.
In addition to the space required for applications, ensure there is sufficient space available on personal vDisks to store users' profiles. Include any non-redirected special folders (such as My Documents and My Music) when calculating space requirements. Existing profile sizes are available from the Control Panel (sysdm.cpl).
Some profile redirection solutions store stub files (sentinel files) instead of real profile data. These profile solutions might appear to store no data initially but actually consume one file directory entry in the file system per stub file; generally, approximately 4 KB per file. If you use such a solution, estimate the size based on the real profile data, not the stub files.
Enterprise file sharing applications (such as ShareFile and Dropbox) might synchronize or download data to users' profile areas on the personal vDisks. If you use such applications, include enough space in your sizing estimates for this data.
The template VHD contains the PvD inventory data (sentinel files corresponding to the master image content). The PvD application area is created from this VHD. Because each sentinel file or folder comprises a file directory entry in the file system, the template VHD content consumes PvD application space even before any applications are installed by the end user. You can determine the template VHD size by browsing the master image after an inventory is taken. Alternatively, use the following equation for an approximately calculation:
template VHD size = (number of files on base image) x 4 KB
Determine the number of files and folders by right-clicking the C: drive on the base VM image and selecting Properties. For example, an image with 250,000 files results in a template VHD of approximately 1,024,000,000 bytes (just under 1 GB). This space will be unavailable for application installations in the PvD application area.
During PvD image update operations, enough space must be available at the root of the PvD (by default, P:) to merge the changes from the two image versions and the changes the user has made to their PvD. Typically, PVD reserves a few hundred megabytes for this purpose, but extra data that was written to the P: drive might consume this reserved space, leaving insufficient space for the image update to complete successfully. The PvD pool statistics script (located on the XenDesktop installation media in the Support/Tools/Scripts folder) or the PvD Image Update Monitoring Tool (in the Support/Tools/Scripts\PvdTool folder) can help identify any PvD disks in a catalog that are undergoing an update and that are nearly full.
The presence of antivirus products can affect how long it takes to run the inventory or perform an update. Performance can improve if you add CtxPvD.exe and CtxPvDSvc.exe to the exclusion list of your antivirus product. These files are located in C:\Program Files\Citrix\personal vDisk\bin. Excluding these executables from scanning by the antivirus software can improve inventory and image update performance by up to a factor of ten.
Consider allowing extra (either a fixed amount or a percentage of the vDisk size) to the total size to accommodate unexpected application installations that the user performs during deployment.
You can manually adjust the automatic resizing algorithm that determines the size of the VHD relative to the P: drive, by setting the initial size of the VHD. This can be useful if, for example, you know users will install a number of applications that are too big to fit on the VHD even after it is resized by the algorithm. In this case, you can increase the initial size of the application space to accommodate the user-installed applications.
Preferably, adjust the initial size of the VHD on a master image. Alternatively, you can adjust the size of the VHD on a virtual desktop when a user does not have sufficient space to install an application. However, you must repeat that operation on each affected virtual desktop; you cannot adjust the VHD initial size in a catalog that is already created.
Ensure the VHD is big enough to store antivirus definition files, which are typically large.
Specifies the minimum size (in megabytes) of the application part (C:) of the personal vDisk. The new size must be greater than the existing size but less than the size of the disk minus PvDReservedSpaceMB.
Increasing this value allocates free space from the profile part on the vDisk to C:. This setting is ignored if a lower value than the current size of the C: drive is used, or if EnableDynamicResizeOfAppContainer is set to 0.
Default = 2048
Default = 1
This setting retains the profiles in C:\Users instead of redirecting them to the vDisk, and lets the roaming profile solution handle the profiles.
This value ensures that all of the space on P: is allocated to applications.
It is assumed that if this value is set to 0, a profile management solution is in place. Disabling profile redirection without a roaming profile solution in place is not recommended because subsequent PvD reset operations result in the profiles being deleted.
Do not change this setting when the image is updated because it does not change the location of existing profiles, but it will allocate all the space on the Personal vDisk to C: and hide the PvD.
Configure this value before deploying a catalog. You cannot change it after the catalog is deployed.
Default = 1
Sets the split between the application part (C:) and the profile part of the vDisk. This value is used when creating new VMs, and during image updates when EnableDynamicResizeOfAppContainer is set to 0.
Changing PercentOfPvDForApps makes a difference only when EnableDynamicResizeOfAppContainer is set to 0. By default, EnableDynamicResizeOfAppContainer is set to 1 (enabled), which means is that the AppContainer (which you see as the C drive) only expands when it is close to being full (that is, dynamic) - when less than 10% free space remains.
Increasing PercentOfPvDForApps only increases the maximum space for which the Apps portion is allowed to expand. It does not provision that space for you immediately. You must also configure the split allocation in the master image, where it will be applied during the next image update.
If you have already generated a catalog of machines with EnableDynamicResizeOfAppContainer set to 1, then change that setting to 0 in the master image for the next update, and configure an appropriate allocation split. The requested split size will be honored as long as it is larger than the current allocated size for the C drive.
If you want to maintain complete control over the space split, set this value to 0. This allows full control over the C drive size, and does not rely on a user consuming space below the threshold to expand the drive.
Default = 50% (allocates equal space to both parts)
Specifies the size of the reserved space (in megabytes) on the vDisk for storing Personal vDisk logs and other data.
If your deployment includes XenApp 6.5 (or an earlier version) and uses application streaming, increase this value by the size of the Rade Cache.
Default = 512
Valid only for XenDesktop 5.6 - Allows the specified group of users to reset a Personal vDisk. Later XenDesktop releases use Delegated Administration for this.
Windows 8 Store needs this service to run to install any Modern-style application.
Some software might conflict with the way that PvD composites the user's environment, so you must install it on the master image (rather than on the individual machine) to avoid these conflicts. In addition, although some other software might not conflict with the operation of PvD, Citrix recommends installing it on the master image.
Size the write cache disk correctly. During normal operation, PvD captures most user writes (changes) and redirects them to the personal vDisk. This implies that you can reduce the size of the Provisioning Services write cache disk. However, when PvD is not active (such as during image update operations), a small Provisioning Services write cache disk can fill up, resulting in machine crashes.
Citrix recommends that you size Provisioning Services write cache disks according to Provisioning Services best practice and add space equal to twice the size of the template VHD on the master image (to accommodate merge requirements). It is extremely unlikely that a merge operation will require all of this space, but it is possible.
The Provisioning Services test mode feature enables you to create a test catalog containing machines using an updated master image. If tests confirm the test catalog's viability, you can promote it to production.
Use the rules files to exclude files and folders from the vDisks. You can do this when the personal vDisks are in deployment. The rules files are named custom_*_rules.template.txt and are located in the \config folder. Comments in each file provide additional documentation.
When you enable PvD and after any update to the master image after installation, it is important to refresh the disk's inventory (called "run the inventory") and create a new snapshot.
Because administrators, not users, manage master images, if you install an application that places binary files in the administrator's user profile, the application is not available to users of shared virtual desktops (including those based on pooled machine catalogs and pooled with PvD machine catalogs). Users must install such applications themselves.
For master images based on Windows XP that you plan to deploy with Personal vDisks, check that no dialog boxes are open (for example, messages confirming software installations or prompts to use unsigned drivers). Open dialog boxes on master images in this environment prevent the VDA from registering with the Delivery Controller. You can prevent prompts for unsigned drivers using the Control Panel. For example, navigate to System > Hardware > Driver Signing, and select the option to ignore warnings.
You can export an inventory to a network share and then import that inventory to a master image. For details, see Export and import a PvD inventory.
The Citrix Broker Service controls the power state of the machines that provide desktops and applications. The Broker Service can control several hypervisors through a Delivery Controller. Broker power actions control the interaction between a Controller and the hypervisor. To avoid overloading the hypervisor, actions that change a machine’s power state are assigned a priority and sent to the hypervisor using a throttling mechanism. The following settings affect the throttling. You specify these values by editing a connection (Advanced page) in Studio.
Default = 100 absolute, 20%
Default = 50 absolute, 25%
To calculate the absolute value: determine the total IOPS (TIOPS) supported by the end-user storage (this should be specified by the manufacturer or calculated). Using 350 IOPS per VM (IOPS/VM), determine the number of VMs that should be active at any given time on the storage. Calculate this value by dividing total IOPS by IOPS/VM.
For example, if the end-user storage is 14000 IPS, the number of active VMs is 14000 IOPS / 350 IOPS/VM = 40.
Default = 10
System Center Configuration Manager (Configuration Manager) 2012 requires no special configuration and can be installed in the same way as any other master image application. The following information applies only to System Center Configuration Manager 2007. Configuration Manager versions earlier than Configuration Manager 2007 are not supported.