Every month go fetch the old hard drives, copy all the new data onto them, then take the currently in use hard drives and put those back into storage. If you w

Every month go fetch the old hard drives, copy all the new data onto them, then take the currently in use hard drives and put those back into storage. If you want more redundancy replace 2x 2x3TB drives with 2x NASes each with 3 drives in raid 5 or 4 drives in raid 1.