So how does the Vacuum cleaner figure into the system?

j/k

Very nice setup.

Obviously I hope you are gonna use a headless (linux) system for your backup storage system on that spare computer you are talking about. You can jam in 3+ hard drives into a raid 5 setup for some redundancy in that backup. It is very easy to do and will work really well. I have four 2TB drives in a raid 5 giving me 5gigs of usable storage (1024 crap and file system over head ate up a whole gig!) I use rsync on several of my clients servers to backup data over the internet to this box and that is what I would do if I was doing something in house. It could easily be automated with a script and/or just use a script to fire off the backup when needed.

Hit me up if you need some help with that.