Last week virtualization.info reported about the release of a paper titled: Microsoft Exchange 2010 on VMware vSphere Best Practices Guide by VMware.
On November 9th, the Microsoft Exchange product team responded on that paper with a blog post titled: Answering Exchange Virtualization Questions and Addressing Misleading VMware Guidance.
The first statement the product team makes is that running Exchange high availability configurations within virtualized environments which are part of the Windows Server Virtualization Program (SVVP) is supported (VMware is part of this program). But Microsoft does not support combining Exchange high availability with hypervisor-based clustering, high availability or migration solutions which automatically failover mailbox servers. The supported configurations for Exchange 2010 can be found on Microsoft Technet.
Further quoting:
"…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…"