If you own multiple computers, hard disks and removable drives it would make perfect sense to have an universally accessible combined data storage pool. Free utility software Greyhole does exactly that.
Greyhole uses Samba to create a storage pool of all available hard drives, allowing users to create redundant copies of there files preventing data loss when part of their hardware fails. Users can add and configure as many disk drives (internal, external, USB, e-Sata, Firewire) as they wish in their storage pool whose resulting size will be the sum of total free space in all the included disk drives.
Users are allowed to keep many copies of each file which will be stored in a different hard drive, this strategy acts like an automated backup solution preventing data loss in-case a disk-drive failure occurs.