[libvirt-users] 2 hosts, mirrored VM storage, avoiding conflicting VM instances

Hi, Using libvirt for KVM, experimenting with live migration with the VM on storage shared in a mirrored GlusterFS or an active-active DRBD setup where QEMU/KVM runs on the hosts on both sides of the mirror, the live migration works great. What concerns me is finding a way if possible to prevent a situation where a particular VM is running on both hosts at once. Is there any way within libvirt in this sort of setup to start a VM on mirrored storage from a KVM host on one side of the mirror _only if_ the same VM isn't already running on the other side of the mirror? In a scripting context I can see how to do that check before starting, but not how to prevent virsh or virt-manager from being used to create this bad condition when they're being used directly. Is there some way to set up protection from this within virsh and virt-manager? Or am I into feature request territory? Or is there some other layer at which this can be accomplished? In active-passive DRBD this wouldn't be a danger, since only the active system can see the storage to start the VM. But that wouldn't support live migration. Part of the danger can be avoided by using stonith in failover, but it would be nice to find a more fine-grained, subtle approach. Best, Whit