vLuddite

I dunno, I think the free version is pretty generous... it can backup an unlimited number of VMs on a single xen server. I don't know how many physical servers you have to run your 6 VMs cookie, but if its only 1, then you probably don't need to pay anything. Plus, before I got a trial when I was using the free version, I could cheat a bit and temporarily move a VM I wanted to backup onto my pool master.

Yes, well, it is hard to argue with the price of entry (free).

I have and its worked great for me so far. Very simple to use, and the compression is excellent. We're running it in a pilot now, but we considering pulling the trigger.