I've used live migration with KVM within OpenStack and it is really damn awesome to be able to migrate all VM's from a host that needs to be downed for maintenance without causing any downtime.

Users SSH sessions may lag for a second or two, but the connection won't even get dropped.

I tried this a while ago with libbirt-kvm and the most awesome thing was that I could live migrate VMs from AMD to Intel and vice versa. None of the other solutions, like vmware or xen do that, afaik.

On the not so good side is that disk cache needs to be disabled for live migration to work at all. This reduces the iops of the vm by 50-60%.

So you either get high performance or high uptime...

I think you'd generally want the host not to do write caching anyway unless you can afford to corrupt VM disks in case of host power failure.

I suppose a hardware battery-backed write cache might still be safe for live migrations.

Anyone has a solution for Live backups?

Say something that migrates the machine and initiate a shutdown as soon as it hits the other backup server?

oVirt can do this. Essentially, such policies belong to management applications, and oVirt or OpenStack are the places where you should look.