HAing your VMs

Is anyone using some form of highly-available storage for the VMs that recovers gracefully (or even transparently) from storage failover? I'd love to hear success/fail stories.

For example, VMs running on:

- HA NFS from NetApp

- HA NFS from red hat cluster

- glusterfs (using the gluster client)

Probably for critical applications I'll have to go with the typical option of replicated SAN, but as this always means downtime to failover (rescan san/etc), I could consider something less enterprisey for less critical uses (and the lower cost would be a welcome side effect).