Jon Rolls, vice president of product management, Quest Desktop Virtualization Group (, says:

“Terminal Server” or “Remote Desktop Session Host” (new name in Windows Server 2008 R2) is a desktop virtualization technology that uses remote display to send the video from the data center to the user’s access device over the network. However, Terminal Server gives each user a share of a Windows Server desktop environment, which is partially isolated from other users. This enables much higher user densities on each server, but comes at the cost of user freedom and application compatibility.

Is desktop virtualization different from other forms of virtualization?

VDI and server virtualization are in essence the same thing – they are both operating systems running inside a virtual machine, the benefit of which is that you can run multiple copies of an operating environment inside one piece of physical hardware, reducing hardware and energy costs, and also allows for greater flexibility and uptime.

Storage virtualization is a whole different area. Storage virtualization organizes sets of physical hard disks in ways that provide faster performance, better fault tolerance and improved business continuity; and presents these collections of disks to server and desktop operating systems as if they were just one physical hard disk.

Some vendors may lead you to believe VDI is the only answer regardless of your desktop needs. Beware! VDI may not be the most economical server-based desktop and application delivery technology! Terminal Server, blade PCs and application virtualization can all be viable alternatives to VDI, depending on what your users need on their desktops and the functions they serve within your organization. Successful desktop virtualization projects typically divide their user base into classes of user type, and select the type of desktop virtualization most appropriate for each user class to achieve the lowest cost per user.

One cautionary note: there are a growing number of vendors in this space. Early on in market adoption cycles, there is typically the greatest number of vendors trying to “get a piece of the action” with products that are good enough to survive a pilot phase, but do not have the depth of management functionality needed for a full-scale deployment. Many organizations have seen their desktop virtualization software become shelfware as they have failed to see the promised TCO benefits when they moved beyond the pilot phase. The management and automation features are the most important piece in delivering a scalable desktop virtualization project that delivers real cost savings.