personal vDisk FAQ

Q: How does personal virtual Disk work?

A: Unlike traditional Virtual Desktop Infrastructure (VDI) dedicated pooled deployments, where users lose their customizations and personal applications when the administrator alters the base virtual machine, deployments using personal vDisk retain those changes. This means administrators can easily and centrally manage their base virtual machines while providing users with a customized and personalized desktop experience.

Personal vDisk provides this separation by redirecting all changes made to the user’s virtual machine into a separate disk attached to the user’s virtual machine (the personal vDisk). The content of the personal vDisk is blended at runtime with the content from the base virtual machine to provide a unified experience. In this way, users can still access applications provisioned by their administrator in the base virtual machine.

Personal vDisks have two parts, which use different drive letters and are by default equally sized:

• One part comprises C:Users (in Windows 7) or C:Documents and Settings (in Windows XP). This contains user data, documents, and the user profile. By default this uses drive P: but you can choose a different drive letter when you use Desktop Studio to create a catalog with personal vDisks.
• The other part comprises a Virtual Hard Disk file (a .vhd file). This contains all other items, for example applications installed in C:Program Files. By default, this part uses drive V: but is hidden from users; this drive is not displayed in Windows Explorer. You can choose a different drive letter by configuring the Virtual Desktop Agent. For information on this, refer to the Knowledge Center article CTX131432 – How to Change Personal vDisk Drive Letters in XenDesktop.

Personal vDisk supports the provisioning of department-level applications, as well as applications downloaded and installed by the users, including those that require drivers, databases, and PC management software. Should an end-user change conflict with an administrator’s change, personal vDisk provides a simple and automatic way to reconcile the changes.

Additionally, the locally administered applications (such as those provisioned and managed by local IT departments) can also be provisioned into the user’s environment. The end user experiences no difference in usability; personal vDisk ensures all changes made and all applications installed are stored in the vDisk.

Physically, a personal vDisk does not need to be stored with the dedicated pool virtual machine. This frees up high-speed disks for virtual machine storage – the personal vDisk can be placed on a less expensive storage solution, like a file server.

Q: Can multiple Personal vDisk’s be associated with a Virtual Machine for each user?

A: No

Q: Is there a way to increase the size of the Personal vDisk without losing the data already stored there?

A: Yes, by going to the hypervisor console and increasing the Personal vDisk that is attached to the Virtual Machine. Data is never affected when expanding the vDisk.

Q: Is there no way to make changes through Desktop Studio or through policy?

A: There really are no policy related settings. You can modify the drive letter in studio (make the P: drive a different letter). For the V: drive, it can only be changed through registry. Expanding the vDisk is available through a PoSH script or by hypervisor console (resize of Personal vDisk).

Q: Are the user installed applications running from an isolated area (sandbox) like RadeCache, etc.?

A: Yes, Personal vDisk does not affect isolation or interfere with it.

Q: Do we imagine UPM will be used alongside Personal vDisk and has the integration of the two been tested?

A: Yes and Yes. There is a registry setting that also tells Personal vDisk to not cache the profile and save Personal vDisk space. Change “EnableUserProfileRedirection” under “HKLMSoftwareCitrixpersonal vDiskConfiguration” to 0.

Q: Does the UI give a warning if a value of 3GB or less is entered for the Personal vDisk?

A: Yes.

Q: Are the Differencing and Identity disks linked to the pooled Virtual Machine, whereas the Personal vDisk is linked to the user?

A: Not exactly. Personal vDisk is assigned/attached to given Virtual Machine, and then the user is assigned a Virtual Machine (that is, pooled static pool).

Q: We do not build a “vDisk” as such rather the resource file/catalog. Correct?

A: The Personal vDisk is the VHD attached to the Virtual Machine through hypervisor. The inventory captures what files, folders and registry data are in the base image and is then stored in the base image (during the initial inventory run when creating the base image); and then is copied to the Personal vDisk in order to track ‘things’ on the Personal vDisk versus what is sourced from the base image.

Q: How much does this add to the Virtual Machine start time?

A: Inventory only occurs in base image preparation (not a user impact) and on first initial start, after an image update has occurred (reconcile between old base, new base and user’s Personal vDisk). This time can take 10-15 minutes or more, depending on how much change has occurred. Desktop Studio/the broker will have the Virtual Machine in a ‘preparing’ state during this time. Once finished, it will be ready for user logon. After this initial start, the start time is increased by a mere 1-2 seconds.

Q: Do we support Personal vDisk on ESX?

A: Yes, Personal vDisk is supported on HyperV, XenServer and ESX.

Q: Is that the same “full copy” process as Machine Creation Services (MCS) would do without Personal vDisk?

A: Personal vDisk does not change the base image/snapshot processing of Provisioning Server

or MCS.

Q: Is Personal vDisk similar in concept to the Provisioning Server set of steps of creating a vDisk?

A: No. Base image management is the same as before with Provisioning Server and Machine Creation Services. vDisk is merely an empty VHD mounted on the hypervisor that captures the writes to the base image. Nothing is really required to prepare other than the initial catalog/inventory.

Q: What happens if the user installs or copies something that goes beyond the size of the disk?

A: User gets Window error – warning about low disk space.

Q: Can we do a “Personal vDisk restore” to a Virtual Machine?

A: Backup and restore need to be done on the hypervisor storage level. You cannot backup/restore at the OS level, since everything will ‘look’ like it is in the Personal vDisk. Thus, restore would populate everything back on to the Personal vDisk. You should backup the VHD from the hypervisor storage and restore the same way, and then reattach to the Virtual Machine through the Hypervisor console.

Q: What happens when you use the V: drive for the default P: – since it is one of the options? Do we need to modify the registry manually or a new drive letter gets assigned for the hidden drive?

A: The P: drive might be changed in Desktop Studio. The V: drive might be changed in base image through registry (CTX131432 – How to Change Personal vDisk Drive Letters in XenDesktop). Drive conflicts leads to failures.

Q: What is the minimum size of the Personal vDisk?

A: 3 GB. If the Personal vDisk size is less than 4GB then the rule of 50% for applications and 50% for profile won’t be applied. If the Personal vDisk is set to less than 3 GB, when the user logs on to the pool environment for the first time, a warning message is displayed that Personal vDisk is not available. *ML* this assumes you can even attach a 3GB Personal vDisk, which is not possible.

Q: What happens if the Personal vDisk Service goes down is the Virtual Machine usable?

A: It depends on which mode you are operating:

• In base Virtual Machine mode it will be useless since the service creates the inventory.
• In pool Virtual Machine mode the machine Personal vDisk would still start but you lose some functionality like the workspace reset feature, etc. (not supported).

Q: Can you commit Personal vDisk changes to the base image?

A: No, there is not a mechanism to do that.

Q: What happens if you have a conflict, same files with identical time stamps or same files with different time stamp?

A: If Personal vDisk detects that exact the same content will be installed – during the image update operation Personal vDisk saves space for that redundancy, and removes the Personal vDisk Adobe Reader and use the one from the base image.

Q: Can the Personal vDisk temporarily be set to read only?

A: No, not yet.

Q: Is Windows 8 on the road map to be supported?

A: Yes.

Q: Any plans to support physical machines for Provisioning Server?

A: Immediate focus will be Virtual Desktop Infrastructure only.

Q: What is captured on the V: drive and what is capture on the P: drive?

A: The VHD created using the template is mounted as V: drive and is it hidden by default. The V: drive is where the apps and machines state is capture. When resetting the Personal vDisk you are resetting the V: drive. The VHD mounted as P: drive is the physical disk that is attached to the hypervisor (to the Virtual Machine).

Q: What about the page file?

A: The Personal vDisk ignores the pagefile, you do not want the Personal vDisk file with the pagefile. It stays on the differencing disk, etc.

Q: Can Personal vDisk be monitored by EdgeSight?

A: There is nothing related to Personal vDisk being monitored by EdgeSight at the moment.

Read the original post on the Citrix Knowledgebase here.

You can find a complete PDF file here over the personal vDisk FAQ.