The second post on the Microsoft Virtualzation Team Blog about Quick Migration and VMotion was added a few days ago. It is mostly a discussion about how VMware HA and Quick Migration both provide a failover solution for UNplanned downtime. I agree with Jeff that both do basically the same thing in the event of an unplanned server outage - the VM is moved to another server and restarted.

The difference that he doesn't talk about is that the rules of the failover are different because of the underlying filesystem that is used in each solution. Microsoft Hyper-V and Quick Migration are using the tried and true Microsoft failover-clustering, which uses an NTFS filesystem on the shared storage. As this is not a cluster file system, the shared storage is actually only visible to one of the servers at a time to prevent corruption. VMware ESX server and VMware HA are working with VMs that are on a VMFS file system which is cluster aware - meaning that multiple ESX servers are able to access the files (or VMs in other words) at the same time.

So following a failure of a Hyper-V server, all VMs on the same disk (or LUN) must be recovered on the same server because the LUN or disk can only be used by one server at a time. In the event of a failure of an ESX server, the VMs can be restarted on any ESX server that has access to the LUN. In order to achieve this flexibility with Hyper-V and Quick Migration it would be necessary to have each VM on it's own LUN. This isn't impossible, but could be more complex to setup and manage.

The end result would be same - the VMs would be restarted on another server. Some of the underlying details can make a difference with flexibility in where those VMs end up.

Todd