Some Exchange-supported virtualization platforms, such as Hyper-V and VMware include features that support the clustering or portability of guest virtual machines across multiple physical root machines. Examples of host-based failover clustering and migration include Hyper-V Live Migration and VMware ESX vMotion.
Microsoft support for host-based failover clustering and migration virtualization with Database Availability Groups (DAGs) depends on the Exchange 2010 service pack level. Per the Exchange 2010 System Requirements:
With Exchange 2010 RTM:
Microsoft doesn't support combining Exchange high availability solutions (such as 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. DAGs are supported in hardware virtualization environments, provided the virtualization environment doesn't employ clustered root servers, or the clustered root servers have been configured to never failover or automatically move mailbox servers that are members of a DAG to another root server.
With Exchange 2010 SP1 (or later) deployed:
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.
In summary, Exchange 2010 SP1 or better supports hypervisor migrations such as Hyper-V Live Migration and VMware ESX vMotion for DAG member servers. Host-based failover cluster migrations, such as Hyper-V Quick Migration, is supported only if the virtual Exchange DAG server is restarted immediately after the quick migration completes. Exchange 2010 RTM is not supported with either migration technology. RTM only supports the native Exchange high availability features present in DAGs.
Other Exchange Server 2010 roles (CAS, Hub Transport, Edge Transport, and Unified Messaging) fully support host-based failover clustering and migration because they do not employ native Exchange high-availability solutions.
For a list of the virtualization platforms supported by Exchange, visit the Windows Server Virtualization Validation Program website.