• The Unified Messaging server role is supported in a virtualized  environment. Combining Exchange 2010 high availability solutions (database availability groups (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, is now supported.   Read more here http://blogs.technet.com/b/exchange/archive/2011/05/16/announcing-enhanced-hardware-virtualization-support-for-exchange-2010.aspx