VMware published a whitepaper about Exchange Server 2003 performance on VI3. It is an interesting read because it shows that it is perfectly feasible to run Exchange Server 2003 boxes with 1000-2000 or more users. Loadsim was used to do the testing so you have to factor in some extra headroom for antivirus and backup procedures. The whitepaper also shows that the virtualization overhead is mainly for the CPU and not for other components such as storage and networking. Because Exchange Server 2003 is effectively limited to 4GB, you can drive up utilization by using a large VMware box with 16GB of memory and lots of cores and run multiple virtual machines with Exchange. Of course, that is the technical side. Many of our customers still don't feel at ease with putting such a critical piece of their infrastructure on a virtual machine but I guess that will change over time.

Of course, it would be more interesting to see Exchange Server 2007 performance on VI3 because Exchange Server 2007 is so radically different from its predecessor. Exchange Server 2007 is a 64-bit app so it does not have the memory limitations of Exchange Server 2003. I hope they will publish a whitepaper about Exchange Server 2007 soon.

Get the whitepaper here.