Since we added Live migration to Server 2008 R2 and Hyper-V R2 Server, I have had numerous requests from people wanting an official guide to the networking configuration requirements for optimal performance and reliability.
The good news is that the guide has now been released and can be downloaded from here: http://technet.microsoft.com/en-us/library/ff428137(WS.10).aspx
We also released a guide recently on using Live Migration with Cluster Shared Volumes in Windows Server 2008 R2. It can be found here: http://technet.microsoft.com/en-us/library/dd446679(WS.10).aspx
For those of you not sure what Live Migration is…
Live migration overview
Live migration is a new Hyper-V feature in Windows Server 2008 R2, which requires the failover clustering feature to be added and configured on the servers running Hyper-V. Hyper-V and failover clustering can be used together to make a virtual machine that is highly available, thereby minimizing disruptions and interruptions to clients. Live migration allows you to transparently move running virtual machines from one node of the failover cluster to another node in the same cluster without a dropped network connection or perceived downtime. In addition, failover clustering requires shared storage for the cluster nodes. This can include an iSCSI or Fiber-Channel Storage Area Network (SAN). All virtual machines are stored in the shared storage area, and the running virtual machine state is managed by one of the nodes. For a detailed overview of live migration and the benefits of using it, see Windows Server 2008 R2 Hyper-V Live Migration.