56,000 Seat Production Exchange 2007 Deployment:

An interesting case study on virtualizing Exchange. Some interesting experiences on performance. General picture is - you can do it but don’t under spec the VM, and make sure you have enough physical resources to do it. I think we are moving away from the “low-hanging fruit” conservatism of the last couple of years…

http://www.mikedipetrillo.com/mikedvirtualization/2008/10/56000-seat-prod.html

http://www.rtfm-ed.co.uk/?p=630