Trying to keep up with virtualization technology can be mind boggling.  While I am a sales engineer, when in the office I am charged with setting up multiple test environments in which to run our products.  I have setup XEN Server, XEN Desktop, VMWare VDI and then View, XEN App, App-V, and more.  Soon I will be given one of our old production ESX boxes to add to the test environment.  Since I started at triCerat I have watched Presentation Server become XEN App, VMWare VDI become VMWare View, and now SoftGrid become App-V.  I have found that there seems to be about seven virtualization categories at least.

• Client Hypervisor – Software that installs on a desktop OS, e.g. Windows XP, Windows Vista, Mac OS
• Bare Metal Hypervisor – The hypervisor installs directly on the hardware without any underlying OS.  Offer by some Vendors as an embedded option on servers.
• Software Hypervisor – Requires an underlying OS, e.g. Windows Server 2008.
• Centralized VDI – Virtual Desktops are running on a virtual server of some type.  Clients connect via protocols such as RDP and ICA.
• Client-based VDI – Virtual Desktops are running on the client’s machine using a client hypervisor.  Images can be managed centrally.
• Cloud Computing – A dynamically scalable virtual infrastructure (physical infrastructures are possible) that provides services over the Internet.
• App Virtualization – Applications packages/profiles are created on a central store and then streamed/delivered to the client when needed.

Below is matrix showing where the big three come into play for these technologies.

1 = The open source XEN Hypervisor can be installed on Linux varients.

2 = Microsoft has partners with Citrix and Quest to provide the brokers in their VDI solution.