The Holy Grail of the VDI endpoint is the zero client. Many vendors claim to offer zero-client VDI solutions that in reality are thin clients. The vendors aren't stupid -- they know what they're offering -- but they are using the customers' quest as a marketing ploy to catch your attention. You might give up and assume there is no such thing as a zero-client VDI endpoint, but do not quit the search just yet.
With many administrators focusing on a dying number of Windows XP machines and hoping to resolve the issue by moving to Windows 7 through a VDI solution, the idea is to use the legacy XP systems as their thin client. I'm sorry, but a full-blown PC with Windows installed is not a thin client in any sense of the word. Still, an administrator may not care as long as the "thin client" keeps running and IT can make a connection back to a VDI-based Windows 7 system.
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A thin client takes on many different forms but ultimately includes a CPU, RAM, and local storage and allows for the network connection. Some clients may be higher end (fat or chubby solutions) to provide better graphics solutions and hard drives, making them more like real PCs than thin clients. The whole dilemma with thin clients is that they have hardware requiring support and maintenance logically, not to mention energy and cooling, but also include some form of operating system, such as Windows XP, Windows CE, or a Linux variant. They're as complex as regular PCs. As you can see, "thin" doesn't mean low maintenance.
The real solution is for vendors to provide what they advertise: the zero-client solution. This ultimate VDI solution pushes the computing back on the data center to the greatest degree possible and eliminates the need to support and maintain a desktop thin (or fat) client. The zero client -- a true zero client, that is -- has no operating system, no CPU, and no memory at the endpoint. Certainly those legacy XP boxes don't fall into the category. What would qualify? Monitors and peripherals (mouse, keyboard, USB devices) that connect to the data center without the local processing aspects.
Vendors claiming to work in this zero-client space include Pano Logic, Teradici, ClearCube, Digi, and Wyse. But when you look at their wares, some are actually offering superthin (or ultrathin) clients -- not zero clients.
Who really offers a zero client? Pano Logic does, with its Pano Cube, which is a simple cube that has no CPU, no memory, no OS, no drivers, no software, and no moving parts. It does have connection points for your keyboard, mouse, monitor, audio, USB devices, and so forth, with a network connection back to a VDI-enabled data center. It acts as more of a KVM access device with clients that are, as Tom Hederson recently wrote, "wicked fast." Currently, this solution does require the use of EMC VMware's vSphere (perhaps we will see a Microsoft Hyper-V solution in the future), and it can only provide XP desktops, but a Windows 7 offering is promised for the near future. The expensive VDI back-end requirement could be be a turnoff to some, but the savings from not buying PCs may offset those costs.