Preservation of correspondence

Jim Leonard wrote: As I said, most of the CDs and DVDs that have failed have been entirely unreadable (except usually for the TOC). That suggests to me that no reasonable recovery mechanism exists (given just one exemplar of the data in question). I might be wrong (my sample size of dead media is statistically insignificant as I have a handful of dead CDs and one dead DVDs out of a total in the hundreds), but I think I'm better off sticking with a simple checksum and writing multiple copies of the media (or, as with my email, having so many copies around that losing one costs me nothing ... given that I also keep all that email on disk _and_ regularly copy to an "online backup" on another disk). So for stuff that I backup and care about I rely on the checksums to tell me that my local copy is OK and I rely on having another copy (or copies) handy in case the media goes bad. My only aim is to try to ensure that I can get to the stuff for as long as I care to get to the stuff. If I wanted to make sure the stuff was still available for future generations I would have to do a lot more. For a start I would have to make sure that someone else has a clue what is backed up and where it might be and why it might matter. That last one is my major problem :-) Antonio