Q: Is a Windows Server 2003 and Windows Server 2008 mixed-cluster possible?

A: No. Windows Server 2008 introduces a lot of clustering changes, including Kerberos authentication, no support for parallel SCSI, and a completely modified API that renders Server 2008 clustering incompatible with Server 2003 clustering. There are no rolling upgrades to move a cluster from Server 2003 to Server 2008.

—John Savill