This is a must read if you want to run Windows HPC Server 2008 and Windows Compute Cluster Server 2003 side-by-side. With the release of Windows HPC Server 2008 (HPCS), customers already using Windows Compute Cluster Server 2003 can choose to add new HPCS clusters side-by-side with their existing clusters. This datasheet covers the basic requirements for coexistence.
“Head nodes using WCCS can control compute nodes only in WCCS clusters, and head nodes using HPCS can control compute nodes only in HPCS clusters. Compute nodes in each cluster must be of the same base operating system as the head node - there is no support for mixed WCCS/HPCS clusters. Head nodes of HPCS clusters can be redundant, using Windows Server 2008 Failover Clustering. There is no redundancy support for WCCS head nodes. Individual nodes of a compute cluster can belong to only one cluster - either WCCS or HPCS, but not both,” Microsoft explained in the Windows HPC Server 2008: V1/V2 Compatibility.