Lance Albertson wrote up a great description of how Ganeti Virtualization Manager performed under pressure during a power outage:
Nothing like a power outage gone wrong to test a new virtualization cluster. Last night we lost power in most of Corvallis and our UPS & Generator functioned properly in the machine room. However we had an unfortunate sequence of issues that caused some of our machines to go down, including all four of our ganeti nodes hosting 62 virtual machines went down hard. If this had happened with our old xen cluster with iSCSI, it would have taken us over an hour to get the infrastructure back in a normal state by manually restarting each VM.
But when I checked the ganeti cluster shortly after the outage, I noticed that all four nodes rebooted without any issues and the master node was already rebooting virtual machines automatically and fixing all of the DRBD block devices.
Ganeti is a management layer that makes it easy to set up large clusters of Xen or KVM (or other) virutalized machines. He has written a great explanation of what is Ganeti and its benefits too.
I use Ganeti for tons of projects at work.