Windows Server 8 Preview
High availability in Hyper-V gets several changes in Server 8. Hyper-V replica lets you configure any host to maintain replicas of virtual machines on any other host. In other words, all you need to do replication is two Hyper-V hosts. Once replication is configured, Windows will failover to the replica automatically in the event of failure. Live migration is also improved. There is now no hard limit on the number of live migrations you can carry out simultaneously, and any Hyper-V host can be configured to receive migrated machines.