It's hard to believe it's been over half a year since Microsoft announced its official support policy for running Microsoft Exchange Server in a virtual environment. Since that time, no doubt many of you have jumped on the virtualization bandwagon. I recently spoke with Gaetan Castelein, senior product marketing manager from VMware about what's going on with Exchange virtualization.

According to Castelein, "We've now reached a phase of development where customers are increasingly using VMware to run large, demanding, data-intensive, business critical apps. And Exchange is a really good example of that." Traditional thinking has been that an I/O-intensive application such as Exchange Server would not make a good candidate for virtualization. However, that's one of the myths you'll see debunked in "Virtualization Myths and Misconceptions."

Castelein sited improved performance of ESX Server over the latest two product generations, specifically for CPU and memory scalability and I/O throughput, as well as I/O improvements that were made in Exchange Server 2007, as reasons why the old belief no longer holds. "If you look at all those technology improvements put together, we've basically removed all the performance bottlenecks to putting a mailbox on a virtual machine," Castelein said.

But Castelein goes further, saying "There's actually a performance advantage to running on VMware." Depending on your hardware, this could certainly prove to be true. Exchange 2007 can only utilize as many as eight processor cores, so what happens, say, if your server has 16 processor cores?

With virtualization, "You have the ability to deploy multiple Mailbox \[server roles\] on that one physical device," Castelein said. "And so by deploying those multiple Mailbox instances, you're able to really use the full capacity of that system. So if you take a 16-core box, you can support 16,000 end-user mailboxes with VMware where you could only support 8,000 end-user mailboxes without VMware."

In addition to improved performance and Microsoft's support, Castelein credits the recent uptake for Exchange virtualization to the economy, Exchange Server upgrades, and the increasing complexity of Exchange. "I definitely think that cost reduction plays a big role here," Castelein said. You know, it's the old "infrastructure consolidation and infrastructure efficiency" argument that's long been part of the virtualization discussion.

As far as the complexity of Exchange—well, I imagine that Microsoft felt that separating Exchange tasks into discreet roles would lead to easier management, and I'm sure some people agree with that. But certainly deployment has become more difficult, requiring setting up roles on different servers. That's another big point in favor of virtualization because you can use multiple virtual machines (VMs) on the same physical server, each supporting a different role.

Of course, VMware isn't the only virtualization option for your Exchange environment. Microsoft has a little thing they like to call Hyper-V that's also supported for Exchange 2007, and you can use Microsoft Virtual Server 2005 to virtualize Exchange Server 2003. Be sure to check Microsoft's support policy for all the official rules and regulations about Exchange virtualization.

You can find a list of supported third-party virtualization platforms on Microsoft's Server Virtualization Validation Program web page. VMware has page of Exchange virtualization resources, Deploy Exchange on a Dynamic Platform, where you'll find customer stories, best practices guides, and other helpful information about planning a virtual Exchange infrastructure.

So, who thinks it's time to get Exchange running virtually? Do you have any favorite benefits of virtualizing that you'd like to share? And who feels that email is too critical to trust to a virtual environment under any circumstances? Leave a comment below to let us know what you think.

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