Limitations for using Hyper-V and Failover Clustering
Specific limitations for using Hyper-V and the failover clustering feature are outlined below:
* A maximum number of 16 nodes in the failover cluster are allowed.
* For each node in the failover cluster, you can have a maximum number of 64 virtual machines for server computer virtualization.
http://technet.microsoft.com/en-us/library/cc732181%28WS.10%29.aspx