A: Virtual machines (VMs) immediately come to mind when most of us think of XenDesktop 5.5, but this solution actually supports five different VM types, in any combination, to create a Virtual Desktop Infrastructure (VDI).
The Dedicated type is perhaps the most obvious. Dedicated VMs are specifically assigned to individual users, and user state persists between log ons. This situation is much different than the Pooled VM type, where a set of VMs is made available to users and user state doesn't persist between log ons.
A third VM type, called Existing, is used when XenDesktop is brought in to manage desktops that have been migrated to VMs in the data center. The fourth type, Physical, enables XenDesktop to manage user desktops on dedicated hardware, which can be any physical machine but is most commonly associated with blade PC hardware.
The final, and most flexible, VM type is Streamed. In this scenario, VMs are provisioned to hardware over the network. This type is commonly used in environments that want VDI's benefits without the cost of its accompanying data center-class hardware.