Microsoft has done a 180-degree turn and decided to support failover clustering for SQL Server running in a virtual machine.
"Last October I posted on our updated policy for support of SQL Server in a virtualization environment," Microsoft Product Manager Bob Ward wrote in a blog post. "One fairly controversial aspect to this policy was our support (actually non-support is a better word) for 'guest' failover clustering. We didn't support installing SQL Server failover clustering in a virtual machine. Well this policy is now changed effective immediately as updated in the article."
Guest failover clustering is when users create a SQL Server failover cluster inside a virtual machine where the nodes are running as a VM. With the change, Microsoft has extended support for this to SQL Server 2005 and SQL Server 2008 in a virtual machine for Windows Server 2008 with Hyper-V, Hyper-V Server 2008 and SVVP (Server Virtualization Validation Program)-certified configurations. The virtual environments must meet the requirements set forth in The Microsoft Support Policy for Windows Server 2008 Failover Clusters, and the operating system running in the virtual machines must be Windows Server 2008 or higher.
Non-SVVP configurations that meet these requirements will receive support as per the policies documented in 897615.
SQL Server 2000 and earlier versions are not supported by the change.