Looks good. The issue here is how to implement that... You would need to somehow mount the remote fs locally (NFS, sshfs, etc) and use vzdump or use two PBS servers on each Dell...
IMHO, I would try to get a third server so you can:
- Have PBS on the 3rd server.
- Have a proper cluster with 2 nodes + qdevice in the 3rd server.
- Do backups of your servers to an external system.
- Even use ZFS (if your raid controller can be run un IT mode or you can replace it, as ZFS does not support RAID controllers) and use storage replication for the two Dell servers.
- Manage all your VMs and backups from one place instead of two.