Is virtualization the wise choice with Exchange 2013?

The past few years (since Microsoft’s support policy officially supported it) all you have heard about is how you should virtualize Exchange.  Virtualize your CAS and Hub Transport roles.  Even virtualize your Mailbox server role but avoid using fixed .vhds and go with SCSI pass-through storage or iSCSI storage (although the Mailbox role is still a heated debate amongst Exchange admins as to whether you should virtualize or not).  The last hold out, the Unified Messaging role, was finally given approval as well and, although it had some strict support requirements (ie it couldn’t be combined with other roles on that machine and it must have at least 4 cores and 16 GB of RAM) it was finally an option.  Virtualization of all roles was now supported and the world was good.

Exchange 2013 a Game Changer

The new architecture of Exchange 2013 moves us down to 2 server roles (not counting the Edge Transport that resides in the DMZ).  The Client Access role handles all connectivity and can certainly be virtualized.  The Mailbox role handles your Mailbox, Hub Transport and Unified Messaging pieces and can also be virtualized.  The question is should you virtualize it?

Well, that is a good question.  For starters, one problem we see with Exchange servers when virtualized is oversubscription.  That means we see folks installing multiple servers on one physical box without providing the physical resources necessary to run those servers properly.  Microsoft doesn’t support this.  If you virtualize Exchange and want their support you must follow the guidance for virtualizing 2010 and 2013 and that is NOT to oversubscribe.

Fair enough.  Well, here is where there is a problem.  What if you want to virtualize your Mailbox role but don’t want to give it such a tremendous amount of CPU and memory due to the bundling in of the Unified Messaging role?  What if you don’t even want to use UM but now feel forced to have a system that is maxed out only for this one role and really, only for the UM side of it, that you don’t plan on using anyway.

No doubt Microsoft will soon have some input in this.  We cannot speak to the support policy side until it is released.  However, you might consider NOT virtualizing this role.  What?!  I know, I know, it’s shocking to hear but look, if you don’t plan on using UM than virtualization requirements may be less stringent, but if you do plan on using UM and running this as a virtualized system than you know it will require quite a bit of hardware resources to function.  That has nothing to do with virtualization, but is part of UM’s need for physical hardware resources.  Servers with the amount of power needed for UM to run smoothly may be costly and put you at a price point where rather than spend all that money on a server that you really are only going to put one virtualized server on (unless you plan on oversubscribing the box… a no-no) than why not just install directly on the system.

We certainly need more information here and I’m sure it will come.  But in talking with some experts at the Microsoft Exchange Conference (MEC) it’s possible some will be shifting back to a non-virtualized environment for their Mailbox/UM role with Exchange 2013.

We will see.