If you have been reading up about the features of Hyper-V 2.0, you probably read about Clustered Shared Volumes or CSVs. Basically, CSVs are the main ingredient to the (not so) secret sauce that makes Live Migration work.
A clustered shared volume can be created from any existing volume in a failover cluster. If you have an existing volume formatted with NTFS, you can mark it as a CSV and it will show up in the Failover Cluster Manager as a CSV. Note that existing data on the NTFS volume is not touched in any way
And now the interesting part: Microsoft did not provide any clear information about how the access to disk is actually performed. Basically the answer to our questions was that the coordinator decides what the best path to the storage is: direct access or over the network. Yes, you read that right: access to the LUN from one node might be redirected over the network via SMB to another node that writes to the LUN. Again, I have no information about when that exactly happens.