While using Provisioning Services(Machine Creation Services) to configure persistent desktops, either through persistent write cache or by attaching a Personal vDisk, is not a very popular approach in large enterprises, there are tons of smaller companied who are interested in this type of setup.
If you talk to Citrix , they would normally suggest you to use PvDs for no more than a 100 to max 125 machines, primarily to prevent things from getting too complicated. If more needed, fully cloned VM’s are preferably used instead.
A Personal vDisk or in short Pvd, offers a way for users to store their changes when working on a virtual, pooled static machine( the PvD is assigned or attached to a VM and then the user assigned a Virtual Machine on first use)
When PVS is used ,streaming is only possible to virtual machines; streaming to physical is not supported. PvD technology can be used with PVS as well as MCS.
Personal vDisk’s can only be assigned to an Desktop Operating System ; server OS are not supported at this time.
Personal vDisk basically stores all changes made under C:\Users as far as user profile concerned and it includes File level, registry changes, installed applications or streamed applications provisioned by SCCM, App-V or XenApp, all user profile(desktop wallpaper, start menu settings, favorites etc..)
The Pvd VHD’s by default , are split in two when it comes to storage collection for Personal (profile-related) and application install/updates. Let’s say if your Pvd is 10 GB in size, it will allocate 5 Gb for Profile(personal storage) and other 5 Gb for application install/updates etc.. This can be changed through Registry Setting into 70/30 ,or 90/10 or 99/1 even…
When administrator updates the image, Personal vDisk will take it from there , the user will be able to see the live changes ,the VM still need a reboot like before Administrator used to roll out changes from studio. It allows all of the user changes to persist over the base image changes.
The Personal vDisk communicates with the XenDesktop Personal vDisk Agent which is installed on the base(Master) image during (Catalog) creation. This agent tracks the changes from installed and the available versus what is changed on the Personal vDisk and will blend these two together once the base image updated and rolled out to end user. This way we get the persistence of dedicated desktops.
If a conflict exists, for example when user installs the same application on his PvD as the Administrator does on the base image, then the system will track & make a note of this change and remove the software installed by user, keeping the PvD as small as possible. Note that this default setting can be customized. PvD’s can be resized afterwards. Their default size and locations are selected during catalog creation wizard when using provisioning method either MCS or PVS.
PvD’s can be attached to any storage target as defined within Hypervisor connection and can be on different storage than your actual VM’s to spread IOPS. PvD’s can be used a simple profile management solution for small sized environments ,although Citrix recommends to use separate profile management solution. PvD’s allow for easier management but with flexibility of dedicated desktops. They are 100% persistent with pooled VD storage and management.