Not very good for long term storage. Specific type of DVD media is more or less OK. <http://adterrasperaspera.com/blog/2006/10/30/how-to-choose-cddvd-archival-media/ <http://adterrasperaspera.com/blog/2006/10/30/how-to-choose-cddvd-archival-media/>> In general the problem is that of obsolescence, the BBC Doomsday Book project was plagued by that. Will there be a mean to reading your media in another 20 years? 30 years? 50 years? I have given up on DVD as storage. I use RAID-1 ZFS volumes which are scrubbed regularly to look for data error. Note RAID-5 in general is NOT recommended for anything that is valuable or a master copy. RAID-5 rebuild is too prone to catastrophic failure. In general, you will have to do regular transcription of the data to successively newer generations of technology over time. Regards Spencer