We've had a number of customers ask us whether or not we support virtualized Exchange Server 2010 deployments. The answer is firmly, YES! We know there are many customers running on under-utilized hardware, and can reduce hardware and maintenance costs by consolidating applications onto a virtualized environment (like the Kentucky Community and Technical College System).

The next question we get asked is what vendor virtualization technology is supported with Exchange. The answer: We support Windows Hyper-V and any vendor listed in the Windows Server Virtualization Validation Program (SVVP). It's as simple as that.

And, lastly, are all virtualized Exchange server configurations supported? Microsoft supports Exchange 2010 in production on hardware virtualization software for all Exchange Server roles except the Unified Messaging role. Moreover, we do support running Exchange high availability configurations within a virtualized environment, but do not support combining Exchange high availability with hypervisor-based clustering, high availability or migration solutions which automatically failover mailbox servers.

Detailed Exchange 2010 System Requirements are maintained on TechNet, and represent the most performant and reliable guidance we can offer our customers. We are continuously expanding our test/production coverage of virtualized Exchange 2010 to expand the supported configurations, and will share any new updates on this blog, as well as the system requirements page on TechNet.

While Microsoft embraces virtualizing Exchange servers because virtualization gives organizations additional choice and deployment flexibility to meet business requirements and lower IT costs, we're concerned by deployment guidance that doesn't accurately follow our Exchange best practices and deployment guidelines. For example, we feel VMware's misleading guidance represented in their recent "Exchange 2010 on VMware Availability and Recovery Options" document (and accompanying "Exchange 2010 on VMware Best Practices Guide") puts Exchange customers at risk, and brushes aside important system requirements and supported configurations. Their guidance could also greatly increase the overall cost of managing your Exchange infrastructure. While we do applaud VMware for leveraging core Exchange Server sizing and performance tools to provide guidance to their customers deploying Exchange Server, our specific concerns are as follows:

Deploying for High Availability

VMware specifically recommends combining their VMware HA solution with the Exchange application-aware high availability solution, which is an unsupported configuration. It is important to note that VMware's HA solution only protects from some hardware failures, while the Exchange high availability solution protects against both hardware and application failures (including a process for patching guest virtual machines). It is simply reckless for VMware to recommend customers deploy this configuration, while ignoring important Microsoft system requirements and unsupported scenarios. In addition, VMware also seems to gloss over the fact that combining these HA solutions will result in new storage requirements that increase cost and complexity. Considering that a significant focus of Exchange 2010 is reducing storage costs, promoting a strategy that increases storage costs isn't consistent with our customers' requirements.

There is nothing within the material that explains how combining Exchange database availability groups (DAGs) with VMware HA will provide a faster end-user mailbox recovery than using Exchange DAGs alone. Since Exchange HA protects against hardware and application failures, it is hard to imagine how VMware can provide a faster, and simpler solution than Exchange HA alone.

Microsoft does not support combining Exchange high availability (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. Microsoft recommends using Exchange DAGs to provide high availability, when deploying the Exchange Mailbox Server role. Because hypervisor HA solutions are not application aware, they cannot adapt to non-hardware failures. Combining these solutions adds complexity and cost, without adding additional high availability. On the other hand, an Exchange high availability solution does detect both hardware and application failures, and will automatically failover to another member server in the DAG, while reducing complexity.

We love that our customers are excited to deploy Exchange Server within virtualized environments. While VMware leveraged Exchange performance and sizing tools to provide guidance, their recommendations casually tiptoe around Microsoft system requirements, unnecessarily increasing storage and maintenance costs and putting customers at risk. Exchange Server 2010 provides choice and flexibility in deployment options. We are committed to virtualization technology deeply, and will continuously review as the various technologies evolve. We hope to do even more in the future with our roadmap. As we work to test and update guidance pertaining to Exchange running under virtualized environments, our current system requirements are in place to give customers the most reliable email infrastructure possible.

Jim Lucey