Virtualizing Exchange Server – what is at the stake?

Michael the author of 4sysops.com posted an interesting post today highlighting the seven disadvantages of virtualization and got me thinking about a critical process we’re currently working on at my IT organization: virtualizing the exchange server.

Reading through Michael’s post reassured my opposition of virtualizing critical applications like exchange server. the first reason is degraded performance. this is what Michael says about performance:

There is no doubt that virtualization requires extra hardware resources. The problem is that it is almost impossible to estimate in advance how many extra resources will be needed. I know that there are capacity planning guides and tools but from my experience every piece of software behaves differently in a virtualized environment. We have applications that are quite modest as long as they run on a physical server, but when they were virtualzed their resource requirement multiplied.

You can’t do much if you have such applications. In our case, we had no choice but leave them on physical servers. Hence, the only solution to this problem is to thoroughly test each application with the virtualization solution of your choice

Even though Michael does not talk about any application in general, I believe Exchange is one of those applications that could behave totally different on a virtualized environment than on a physical server. I guess performance in exchange is affected on how many people will be using it, but with 300 and something mailboxes active on our exchange server this had me thinking.

another important point Michael makes is; complex root causes.

Virtualizing a server certainly implies big changes to the whole system. A new layer of complexity is added and can cause new problems. However, the main difficulty is that if something doesn’t work as it is supposed to, it can require considerable extra efforts to find the cause of the problem.

I definitely agree with Michael on this one. by virtualizing exchange, you are actually adding complexity to the process, and troubleshooting problems that might arise with the application could be a painstaking task.

Another interesting downsize of virtualizing exchange is that its not supported by Microsoft if you are using a different virtualization software rather than Windows Virtual Server 2005 R2 or later version. this is Microsoft Policy regarding this issue:

Microsoft supports Exchange Server 2003 running on hardware virtualization software (virtual machines) only when all the following conditions are true:

• The hardware virtualization operating system is Virtual Server 2005 R2 or a later version.
• The version of Exchange Server that is running on the virtual machine is Microsoft Exchange Server 2003 Service Pack 2 (SP2) or a later
• version.The Microsoft Virtual Server 2005 R2 Virtual Machine Additions are installed on the guest operating system.
• Exchange Server 2003 is configured as a stand-alone server, not as part of a Windows cluster.
• The SCSI driver that is installed on the guest operating system is the Microsoft Virtual Machine PCI SCSI Controller driver.
• The virtual hard disk Undo feature is not enabled.

As you can see, my opposition to virtualizing exchange is founded on a solid ground, but my only voice was not enough to stop the process, so the implementation is on its way, I just hope for the best that we won’t regret it later on.

What do you think? do you think virtualizing exchange is a good idea or not? it would be comforting to hear your ideas.