I believe what you're essentially trying to do would be distributed computing. I would take a look at beowulf clusters. The end result would be that the data is mirrored on the drives, if my memory serves...and you get the benefit of additional computing power from each networked machine.
Here's a link if you're not familiar with it: http://www.beowulf.org/
Other than the above option, I'm not aware of a real-time method to do what it sounds like you are trying to do. A non-real-time solution would be to create NFS shares on the networked machines, and incrementally back the data up on the shares over the network.
Hope this helps.