3. Desktop virtualization and VDI mean pretty much the same thing
VMware was first to promote the VDI (virtual desktop infrastructure) terminology, but Microsoft and Citrix have followed suit, offering VDI solutions of their own based on the Hyper-V and XenServer hypervisors, respectively. Think of it this way: VDI refers to the basic architecture for desktop virtualization, where a VM for each user runs on the server.
4. Don't confuse desktop virtualization with ... desktop virtualization
The desktop virtualization we're talking about refers to server-based computing. But "desktop virtualization" also refers to running virtual machines on desktop systems, using such desktop virtualization solutions as Microsoft Virtual PC, VMware Fusion, or Parallels Desktop. Probably the most common use of this sort of desktop virtualization is running Windows in a Parallels or Fusion VM on the Mac. In other words, this has nothing to do with server-based computing.
5. No server-based computing solution supports the same range of hardware as a desktop
The Windows folks in Redmond spend half their lives ensuring compatibility with every printer, graphics card, sound card, scanner, and quirky USB device. With thin clients, your support for hardware is going to be pretty generic, and some items won't work at all. Other limitations are introduced by the fact that users interact with their VMs over the network. Multimedia, videos, and Flash apps can be problematic.
6. VDI solutions cost more (and deliver more) than traditional thin client solutions
Think about it: With VDI, each virtual machine needs its own slice of memory, storage, and processing power to run a user's desktop environment, while in the old-fashioned Terminal Services model, users share almost everything except data files. VDI also means a separate Windows license for each user, while Terminal Services-style setups give you a break with Microsoft Client Access Licenses. Plus, VDI incurs greater network traffic, which may add a network upgrade to the purchase order for beefy server hardware.
In return for that extra cost, along with a better user experience, VDI delivers greater manageability and availability. As with server virtualization, you can migrate virtual machines among servers without bringing down those VMs, perform VM snapshots for quick recovery, run automated load balancing, and more. And if a virtual machine crashes, that doesn't affect other VMs; with Terminal Services, that single instance of Windows is going to bring down every connected user when it barfs.
7. Dynamic VDI solutions improve efficiency
In a standard VDI installation, each user's virtual machine persists from session to session; as the number of users grows, so do storage and administration requirements. In a dynamic VDI architecture, when users log in, virtual desktops assemble themselves on the fly by combining a clone of a master image with user profiles. Users still get a personalized desktop, while administrators have fewer operating system and application instances to store, update, and patch.
8. Application virtualization eases VDI requirements even more
When an application is virtualized, it's "packaged" with all the little operating system files and registry entries necessary for execution, so it can run without having to be installed (that is, no changes need be made to the host operating system).