There are two new options in Windows Server 2012 Hyper-V to help improve the performance of live migrations. The first (and the new default) is the ability to enable compression on the data to reduce the total number of bytes transmitted over the wire. The obvious caveat is that tapping CPU resources for data compression could potentially impact other operations, so you'll need to take that into consideration. The second option, SMB Direct, requires network adapters that support RDMA. Microsoft’s advice: If you have 10Gb available, use RDMA (10x improvement); otherwise, use compression (2x improvement).