The basic challenge of virtualization, as it affects desktops, is to come up with a clean way of separating a desktop from the files and the preferences that belong to a user.
Virtual Desktop Interface (VDI)
If one installs and then starts with VDI, a user's PC desktop is located on a virtual computer in your datacenter. The user is now able to move between the desktop displays at different locations. The desktop image will then show up on each thin client (or fat client operating in a “thin mode”) and still get the same desktop.
The virtual desktop interface still remains as a monolithic file in which the user's files and the Windows desktop are mashed together. The user may only have a few GB of personal files, but they are entangled with a Windows operating system that is 50GB or more.
Virtual Desktop
In a Virtual Desktop there is a clean separation between the user's files (and all their settings and preferences) and the Windows operating systems. This is accomplished by creating a user “Profile”, which can be centrally stored and is completely separate from the Windows operating system.
In order to use the desktop, one must reattach the “Profile” to the desktop instance of the Windows operating system. In such a case the desktop instance of the Windows operating is completely generic and standard issue from Microsoft. Because the standard issue has no personalization it will be easier to manage because one will need only one master copy.
The separate “Profile” is much cleaner, smaller, and easier to protect than a full virtual desktop.
SUMMARY
Virtualization offers two options how to manage desktops. How they are implemented will depend on how legacy systems will be migrated. The Virtual Desktop should be seen as an easier solution.
In the case of DoD the economic benefits from desktop virtualization exceed the benefits from server virtualization. Potentially there will be well over a million desktops that can be migrated into a much lower cost environment. For this reason the choice how to convert to virtual desktops running on thin clients is important.