[dba-VB] Syncing Virtual Machines

I have a virtual machine server (Colby-VM) and last weekend I rebuilt that machine - new motherboard 
/ memory in preparation for a faster CPU etc.  I store all my stuff on a RAID array on a dedicated 
controller, and which survives nicely across upgrades so I got lazy and did not backup.  (almost) 
Everything that could go wrong did and by the end of the experience I was sweating bullets about 
whether I was going to find one of my critical VMs.

I did get all the VMs back, but this brought me to the question of how the pros migrate machines 
from server to server.  My SQL Server (Azul) has Windows 2008 with Hyper-V installed and I am 
wondering how to cause a VM to be kept synced on two servers so that it can just fire up and go when 
the usual VM server has to be brought down.  Hyper-V has an "export / import" but that takes a 
loooong time to perform.

Is anyone out there involved in this stuff and do you have any answers to this problem?  I would 
love to be able to just shut the machine down on one server and bring it up on the other.  My 
impression is that it is possible to migrate without even shutting down the VM.  How is this magic done?

-- 
John W. Colby
Colby Consulting

Reality is what refuses to go away
when you do not believe in it