tall order this request but I am hopeful...
I have a bunch of servers (exactly 20) that each have about 2-7TB of free space, and that space is not in any danger of being used up soon. I was wondering if there is some application that I can allocate some percentage of that spare disk to and it would would manage replicating the files to be redundantly stored in various places.
I would imagine the distributed network RAID type file-system would present itself much like nfs, and require some lock manager, or centralised management server to facilitate all this or alternatively could use some multicast protocol.
I looked at a few distributed systems like GFS, but they seem to require reformatting which is not an option.