The Unified Messaging role is a fantastic component of Exchange if you’ve got an on-premises phone system and currently have to run a separate voicemail system. The UM feature can not only replace your existing voicemail system, but it can also transcribe the messages into text for you, has great Outlook integration and provides voice access to mail, calendars and your phone directory.

However, it did have a downside. If you’ve considered virtualizing Microsoft Exchange roles in the past and use the Unified Messaging features, you’ve probably seen the following statement direct from the System Requirements document on TechNet:

All Exchange 2010 server roles, except for the Unified Messaging server role, are supported in a virtualization environment. This is due to the real-time response requirements associated with voice communications with the Unified Messaging server role.

So, while Lync is supported in a virtual environment it may have been a disappointment to find that you can’t virtualise a role that, on the face of it, would seem an ideal candidate for virtualization – the Unified Messaging server. Although it can be processor intensive, it’s not especially I/O intensive, nor does it require tons of storage and it can be scaled by the addition of further UM servers, load balanced by your PBX.

Therefore it comes as little surprise to read in the latest Exchange 2010 whitepaper, released just in time for TechEd 2011, “Best Practices for Virtualizing Exchange Server 2010 with Windows Server® 2008 R2 Hyper V“, that the Unified Messaging role is now supported in a Virtual Environment:

Microsoft Exchange Server 2010 SP1 supports virtualization of the Unified Messaging role when it is installed on the 64-bit edition of Windows Server 2008 R2.

Unified Messaging must be the only Exchange role in the virtual machine. Other Exchange roles (Client Access, Edge Transport, Hub Transport, Mailbox) are not supported on the same virtual machine as Unified Messaging.

The virtualized machine configuration running Unified Messaging must have at least 4 CPU cores, and at least 16 GB of memory.

Whilst these are pretty high requirements for a single VM, they certainly aren’t unfeasible, and I certainly don’t think they should be a deterrent to virtualizing the role. Typical hosts for virtualization can typically see 12x3Ghz cores and 196GB of RAM for well under £10K per host.

The only caveat worth bearing in mind is that the document is specifically aimed at Hyper-V; the support statement above just says “virtualization” and of course the associated TechNet article hasn’t been updated either – so it’s certainly worth waiting to see the extra details in TechNet 2011’s session EXL306 and watching the main TechNet Article to see if it’s updated.

Update 16th May – The updated guidance does indeed apply to VMware environments too, as per the Exchange Team Blog:

* The Unified Messaging server role is supported in a virtualized environment.
*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.

Due to improvements we made in Exchange Server 2010 SP1, along with more comprehensive testing of Exchange 2010 in a virtualized environment, we are happy to provide this additional deployment flexibility to our customers. The updated support guidance applies to any hardware virtualization vendor participating in the Windows Server Virtualization Validation Program (SVVP).

BTW– thanks to Tim Harrington for making me aware of this document; I wasn’t expecting the UM news to be made public until next week, so it was a nice surprise!

And if you are interested in Virtualizing Exchange, check out Henrik Walther’s and Michel De Rooij’s blogs for some more more details about support for Live Migration/VMotion and host-based HA support.

Finally, if you’ve got any thoughts, let me know in the comments. If you’ve already been virtualizing the UM role regardless of the support (!) how’s it been? Any problems? If you are virtualizing Exchange Server 2010 at the moment, but still don’t plan on virtualizing the UM role, why not?