if you build a small system, cheapish, an itx with 6sata, each connected to a port multiplier, os on flash... you could have 30tb from 1tb drives. set it all up as an lvm2 volume, then you can slap the drives back in a new system any way you want, and they'll come back up in the right order. rsync(backupmypc) will keep the backup in good condition, you'd of course need spares, in case the verify shows a drive fail, a duplicate system. using linux raid to turn the two nfs mounts into a raid 1 array would be nice, but parity would be better, yet it'd take even more drives. yah, bigger drives would be a good first start.