I wanted to blog some more on recent chats I had at TechEd, particularly with some confusion with Windows Server Virtualization (aka Viridian).  There was a common misconception that Microsoft Virtualization was “very fat“.  So in an attempt to compare ‘apples to oranges‘ I thought I’d put some numbers out there, and put a loose perspective on things.

Firstly Windows Virtualization is not the same as Virtual Server.  Sure they both run Virtual Machines, but I’ll use the analogy of comparing SQL and Microsoft Access.  …you can use your imagination to decide which is which :)

ComparisonVMMAnyway, at the moment we all know that Virtual Server is installed on top of Windows 2003.  So your install footprint consumes ~2 Gb.  Then your Virtual Machines, run on top Virtual Server.  As per the diagram to your right.  >

So lets fast forward a little bit.  Windows 2008 CTP (aka Longhorn) has an install footprint of ~4.4 Gb.  But we don’t need most of that install base to run Windows Virtualization.

So Windows 2008 can also be installed in a mode called ’Windows Server Core‘.  Windows Core is a lean and mean install of Windows without any of the ’bells and whistles‘.  Core has an install footprint of ~1.3 Gb.  Then we need to add the hypervisor and Windows Virtualization role.

The hypervisor is super thin, and installed under Windows.  Although I don’t have numbers I can publish at the moment, think Potato Crisp thin.  Once the hypervisor is installed, your VMs essentially run beside your installation of Windows Core.   again see the diagram above. ^