It's been a few months since we announced some major changes to our virtualization support statements for Exchange 2010 (see Announcing Enhanced Hardware Virtualization Support for Exchange 2010). Over that time, I've received quite a few excellent questions about particular deployment scenarios and how the changes to our support statements might affect those deployments. Given the volume of questions, it seemed like an excellent time to post some additional information and clarification.
First of all, a bit of background. When we made the changes to our support statements, the primary thing we wanted to ensure was that our customers wouldn't get into a state where Exchange service availability might be reduced as a result of using a virtualized deployment. To put it another way, we wanted to make sure that the high level of availability that can be achieved with a physical deployment of the Exchange 2010 product would not in any way be reduced by deploying on a virtualization platform. Of course, we also wanted to ensure that the product remained functional and that we verified that the additional functionality provided by the virtualization stack would not provide an opportunity for loss of any Exchange data during normal operation.
Given these points, here's a quick overview of what we changed and what it really means.
With Exchange 2010 SP1 (or later) deployed:
- All Exchange 2010 server roles, including Unified Messaging, are supported in a virtual machine.
- Unified Messaging virtual machines have the following special requirements:
- Four virtual processors are required for the virtual machine. Memory should be sized using standard best practices guidance.
- Four physical processor cores are available for use at all times by each Unified Messaging role virtual machine. This requirement means that no processor oversubscription can be in use. This requirement affects the ability of the Unified Messaging role virtual machine to utilize physical processor resources.
- Exchange server virtual machines (including Exchange Mailbox virtual machines that are part of a DAG), may be combined with host-based failover clustering and migration technology, as long as the virtual machines are configured such that they will not save and restore state on disk when moved, or taken offline. All failover activity must result in a cold boot when the virtual machine is activated on the target node. All planned migration must either result in shutdown and cold boot, or an online migration that makes use of a technology like Hyper-V Live Migration. Hypervisor migration of virtual machines is supported by the hypervisor vendor; therefore, you must ensure that your hypervisor vendor has tested and supports migration of Exchange virtual machines. Microsoft supports Hyper-V Live Migration of these virtual machines.