Why shouldn't it work? As far as clustering is concerned, they are cluster services which will then be failed over as normal if needed/wanted. As you say, performance could be an issue, but you'll be looking at splitting the resources as necessary so as long as that is ok that should be fine. I don't have Win 2k8r2 for my cluster, but 2k8 has been ***rock*** solid from day one. I cannot see there being any issues there. Are you adding both to a new cluster, or adding SQL Server to a current DB2 cluster?