For those who wish to run Citrix UPM along with Personal vDisks in a XenDesktop / XenApp with PVS, this is immensely helpful
Here is a quick overview of the personal vDisk feature which Citrix acquired from RingCube; its uses, general architecture, installation requirements and other things to consider before deployment. i promise it is a good read.
Personal vDisk Architecture
Personal vDisk Troubleshooting and Support