Not sure if it will fit your needs or not, but for long term storage on single HDs (and back in the day on DVD), I would create par files with about 5-10% redundancy to guard against data loss due to bad sectors. http://parchive.sourceforge.net/ total drive failure of course means loss of data, but the odd bad sector or corrupted bit would be correctable on a single disk. This was very popular back in the binary UseNet days....