[libvirt-users] KVM and RAID1 over IP

Does anyone here have any experience with using KVM/libvirt with RAID1 over IP/DRBD or other HA solution? I'm trying to figure out the hardware configuration I would need to be able to survive a failure or planned shutdown of any one unit in a virtualization cluster. KVM/libvirt makes moving running VM's from one host to another a no brainer, but I'm trying to figure out the right way to be able to take a the storage backend for maintenance without disrupting the VMs. Right now I'm thinking something like KVM + libvirt + heartbeat/corosync + pacemaker + DBRM on Ubuntu 10.04 with 3 or 4 nodes - 2 hosts, 2 storage, or 1 host, 1 host + storage, 1 storage. Any thoughts? Thanks!