A month ago I went into some detail on Windows Server 8 Hyper-V Live Migration. In short, Live Migration has been removed from Failover Clustering and is possible between clustered and non-clustered hosts. The VMs can be on a SAN or on an SMB 2.2 file share (or Scale Out File Server/SOFS). The VMs can also reside on internal disk/DAS on the host. This can take advantage of Live Storage Migration to move the VM (process, memory, CPU) and its storage (VHD or VHDX), if you want, to the new host. There’s nothing like a demo to illustrate this:
In this demo, I move a running VM from Host1 to Host2, both running Windows Server 8 Beta. The only networking is a single 1 GbE NIC. I ping the VM, move it, and double check that (a) there is no network loss (normally you expect 1 ping to be lost in the UDP-based ping, but TCP would tolerate this) and (b) the VM is still running.