A. VSS Backups will be supported with CSV in Server 2008 R2, but remember how CSV works. You have one node in the cluster that is the coordinator node for a volume and the other nodes in the cluster perform direct I/O at a block level.

When you need to create a point-in-time backup of a CSV volume, you must create a stable environment. Conducting backups of a CSV volume requires special considerations and new APIs that backup applications must use to work in a CSV environment. When a backup of a CSV volume is initiated on a Hyper-V Cluster node, that particular CSV volume must be locally mounted on (or moved to) the machine running the backup. In addition, all remote application disk I/O to and from the CSV volume is re-routed over Server Message Block for the duration of the backup, instead of using direct I/O. Backup applications that haven't been modified to use the new VSS API will not be able to safely backup a CSV volume. Microsoft is working with the ISV and independent hardware vendor communities to evangelize the changes required for CSV Backup/Restore. You should verify with your backup vendor that they explicitly support CSV by using the new PrepareVolumeForSnapshotSet API call.

See also:
How do I create a failover cluster in Windows Server 2008?
Is a Windows Server 2003 and Windows Server 2008 mixed-cluster possible?
How can I add disk resources to a Windows Server 2008 cluster from the command line?
How do cluster shared volumes work in Windows Server 2008 R2?

How to Manage Failover Clusters in Windows Server 2008
Configure Windows Server 2008 Failover Clustering from the Command Line

Check out hundreds more useful Q&As like this in John Savill's FAQ for Windows. Also, watch instructional videos made by John at ITTV.net.