On May 16, Microsoft took advantage of the start of TechEd North America (the marketing folks always like to have news to reveal at major conferences) to make a significant announcement about virtualization support for Exchange 2010. The two biggest and most welcome changes are outlined as follows:

“As of today, the following support scenarios are being updated, for Exchange 2010 SP1, and later:

• The Unified Messaging (UM) server role is supported in a virtualized environment. [if running Exchange 2010 SP1 – Exchange 2010 RTM is not supported]
• Combining Exchange 2010 high availability solutions (database availability groups (DAGs)) with hypervisor-based clustering, high availability, or migration solutions that will move or automatically failover mailbox servers that are members of a DAG between clustered root servers, is now supported.”

The fact that UM servers are now supported in a virtualized environment is good but hardly earth-shattering, simply because UM remains well behind the other server roles when it comes to prioritization for deployment. In addition, having sufficient CPU to process inbound voicemail (to generate voicemail previews, for instance) has always been the traditional concern about virtualizing the UM role. This concern still exists if you are in a situation where a high volume of voicemail  must be processed. The normal rule of thumb is that a second of voicemail takes a second of CPU core to process so it’s relatively easy to figure out whether sufficient CPU power can be made available to deal with the expected volume of voicemail. According to Microsoft at TechEd, a 4 vCPU server with 16GB of memory can handle 40 incoming calls, so that’s another figure to keep in mind.

Despite some caution on my part, virtualization support for UM servers is a welcome advance as it lifts another barrier that might stop customers trying out Exchange UM. It’s worth noting here that new features in Exchange 2010 UM make it worth another look if you’ve passed on it before. Voicemail preview and MP3 codec support make it much easier to access voicemail on the run and there are many other tweaks over what was delivered in Exchange 2007.

Of course, voicemail preview only works if you run one of the seven languages that UM supports. Quite logically, Microsoft only adds languages when it is confident enough that sufficient data is available to allow UM to do a reasonably accurate job of transcribing voicemail to text or understanding human prompts. I’m not all that annoyed that Irish-English (en-ie) isn’t supported yet as there are many strange and wonderful words and phrases that we use in conversation here that are not found elsewhere.

Getting back to virtualization, the fact that “The updated support guidance applies to any hardware virtualization vendor participating in the Windows Server Virtualization Validation Program (SVVP)” means that both VMware and Hyper-V are supported, which is more good news, and Microsoft has released an updated white paper to provide advice and guidance about how best to deploy Exchange 2010 on Hyper-V running on Windows 2008 R2. No doubt VMware will have their own take on the subject in the near future.

Of course, the big news in the announcement is that DAGs are supported when they are layered upon the high availability features enabled in a virtualized platform. The previous advice was to avoid clashes between the high availability features of Exchange 2010 and those provided by the virtualized platform. In other words, you didn’t want to get into a situation where Active Manager attempted to do a failover of a database or complete server and clashed with some servers that were being moved around by the underlying platform.

I think that it will take time (and probably some failures in production scenarios) before the magic formula for co-existence between Exchange 2010 DAGs and the various hypervisors emerge. In the interim, the best advice is to keep designs as simple as possible and then test, test, and test again before you deploy any configuration into production.

– Tony