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How Microsoft's new support policy for virtualized Exchange will affect you

Whether you're evaluating virtualizing Exchange Server or you're testing it in production, Microsoft's new support policy will affect you. Get honest analysis of the new support guidelines from Exchange Server virtualization expert David Davis. You'll also learn 10 specific virtualized Exchange conditions that you must follow.

Are you considering running Microsoft Exchange Server in a virtualized environment? Or are you pushing the possibilities of virtualization, and already running Exchange virtualized in a large production environment? Either way, new changes to how Microsoft supports Exchange when it is virtualized may affect you.

What is Microsoft's new support policy for virtualized Exchange?
Recently, Microsoft released its official support policy for those running Exchange Server in a virtualized environment. In other words, if you pay for support from Microsoft for your Exchange mail server and you opt to virtualize that server, you must follow this policy to receive full support. This is not a short policy, by any means.

First, I want to take a second to commend Microsoft on supporting Exchange Server in a virtualized environment. While the company could have done it sooner, it also could have waited much longer. I think that by recognizing that virtualized Exchange environments should be supported, Microsoft will prompt other vendors to offer official support for their applications in a virtual environment.

Microsoft's support policy is very restrictive and very detailed. It tells you what virtualization platform to use, what type of virtual disk, levels of service packs that must be applied, limits on what software can be installed on the host and the guest, high availability and disaster recovery recommendations, backup/restore considerations, and more.

While this policy may seem overly restrictive at first, I can understand why Microsoft needed to be specific when it comes to supporting virtualized Exchange installations. After all, virtualization's dynamic nature allows you to share hardware and migrate servers in seconds -- features that can complicate troubleshooting problems.

Additionally, Microsoft's policy is very detailed. Following are 10 specific virtualized Exchange conditions that I learned from the policy.

Note: You can read the official policy, Microsoft support policies and recommendations for Exchange servers in hardware virtualization environments, at Microsoft's website.

What are 10 specific virtualized Exchange conditions that you must follow?
To simplify Microsoft's complex policy, here are 10 conditions that you must follow in order to obtain support for your virtualized Exchange server:

  1. Install your server only on Microsoft Hyper-V or a virtualization platform that the Windows Server Virtualization Validation Program (SVVP) covers. In other words, Exchange is not supported on Microsoft Virtual Server 2005 or Virtual PC.
  2. Exchange Server 2007 must be running SP1 (or greater) and be running on Windows Server 2008.
  3. The Unified Messaging (UM) role cannot be installed on this Exchange server. (It's a good thing that we have virtualization or another physical server could cost us a bundle just to fulfill this requirement.)
  4. You must use fixed virtual disks, SCSI pass-through (raw disks) or iSCSI storage. This means that if you put your virtual Exchange server on a dynamic disk, Microsoft may not support it.
  5. Differencing or delta disks are not supported.
  6. No server-based applications -- except for antivirus, backup software or virtual machine management software -- can be installed on the host system.
  7. Combining clustering solutions is not allowed. While this point could use further explanation from Microsoft, I understand it to say that you cannot use both replication AND Exchange clustering.
  8. The creation of an Exchange snapshot is not supported.
  9. The virtual-to-logical processor ratio cannot be greater than 2:1.
  10. Use of Hyper-V's quick migration is not recommended and can cause data loss.

I find it strange that virtualization snapshots are not supported. Snapshots are major Hyper-V virtualization features. Suppose that you're upgrading to Exchange Server Service Pack 5, for example. Best practices dictate that you should take a point-in-time snapshot of that virtual Exchange server prior to the upgrade in the event that the service pack trashes your Exchange server. However, Microsoft is officially saying NOT to use snapshots because they aren't application-aware. What if you shutdown the Exchange services to quiesce the data, and then took a snapshot? You would think that, in such a case, your Exchange data would be fine and snapshots would be an excellent data-protection feature. Unfortunately, Microsoft offers no guidance on the proper and supported use of snapshots, except to say that they aren't supported.

Also, Hyper-V quick migration is listed as "not recommended." Instead, Microsoft recommends that you use cluster continuous replication (CCR). Again, quick migration is a major Hyper-V feature. I wonder what Microsoft would say about using VMware's VMotion with live Exchange data. I have used it many times on production servers without data loss.

Another recent development related to quick migration, VMotion, and the movement of virtualized Exchange servers is that Microsoft is waiving its 90-day license reassignment policy to enable customers who virtualize Exchange to move their licenses between servers within a data farm as often as necessary. This makes sense to me. If you own the Exchange license, you should be able to use it on whichever server you want, whenever you want.

These 10 conditions are just a small part of Microsoft's policy. There are still many more conditions and recommendations to consider. I recommend reading the full policy to learn more.

Will Microsoft "put you through the wringer" when you call for Exchange support?
As I said before, I can understand the need for a specific supported configuration for virtualized Exchange servers. On the other hand, from the IT pro perspective, I fear that Microsoft could make an experienced IT pro who has virtualized Exchange completely prove that they have met every one of these specific configurations -- before offering them any support.

In other words, if you call with a generic question on new Exchange Server 2007 antispam features, will Microsoft support force you to prove that you aren't using dynamic disks and you don't have any antispam software installed on the host virtual server, before answering your question?

In the end, the results of this policy are that IT pros need to be careful when they configure their virtualized environment. And we will only know, from the feedback of real customers calling for Exchange Server virtualization support, how strictly Microsoft applies these configuration requirements to each call.

What is Microsoft's policy for supporting Exchange when virtualized with VMware?
I have experience with running Exchange Server 2007 in a VMware ESX Server virtual environment (see my story, Upgrading Exchange Server? Migrate to ESX). When the IT pros in my group decided to move to Exchange 2007 and virtualize it with VMware ESX, we knew that it was risky. We knew that Microsoft could choose to not provide support for Exchange if we called and they found out that our servers were virtualized.

Still, we felt that most of the support calls we made were just feature-related and the topic of virtualization would never come up. Overall, we felt it was worth the risk.

VMware was the first non-Microsoft virtualization hypervisor to be validated under the Microsoft Server Virtualization Validation Program. In VMware's official SVVP announcement, the company discussed how IT pros can officially receive support from Microsoft if they are running VMware ESX Server 3.5 MU2. Microsoft and VMware will have high-level support groups that can work together to alleviate issues between them.

This is an excellent step for both VMware and Microsoft that will tremendously benefit IT pros who want to use VMware's ESX Server virtualization hypervisor. According to VMware, the University of Plymouth in England is already running 50,000 mailboxes in VMware ESX Server. This trounces my store of my 1,500 mailboxes, but it still makes a point that Exchange running in a virtualized environment simply works.

IT pros that were waiting to virtualize Exchange Server because Microsoft didn't officially support it can no longer use that excuse. The time to virtualize Exchange has never been better. Still, when you do it, make sure that you read and follow Microsoft's conditions thoroughly so you don't run into any performance or support issues. While Microsoft's policy is long, complex and strict, it is also a great way to protect yourself and ensure that your virtual Exchange server is solid and supported.

About the author: David Davis (CCIE #9369, VCP, CWNA, MCSE, CISSP, Linux+, CEH) is the Director of Infrastructure at Train Signal Inc. He has written hundreds of articles and six video training courses, including the Train Signal VMware ESX Server video training series. His websites are and


We are in the planning process for migrating to Exchange Server 2007 SP1. We were concerned that Microsoft wouldn't offer any level of support unless we had the $50,000 per year Premier Support Plan, which almost no company can afford. There is no question we are going to virtualize our new Exchange 2007 server.

You mention the statement below, but you don't go into great detail. Can you explain what you mean?

The virtual-to-logical processor ratio cannot be greater than 2:1.

Does this mean that if we have four quad core processors on our ESX host servers, we can't assign more than X number of CPUs to the Exchange 2007 VMware virtual machine?

Or does it mean that we can only have X number of VMs running on the same ESX host as the Exchange 2007 VM?

Any information would be very helpful.
- Clayton M.


Say that you had four quad core processors. That is 16 logical processors (4x4). Thus, you could not assign more than 32 virtual processors to guest virtual machines on that server. In other words, the virtual to logical processor ratio would be 32:16 or 2:1, which Microsoft said you could not exceed. I hope that helps clarify.
- David Davis, article author

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