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> the metallic mirror will oxidize after a few years and the disk will become impossible to read. I think NIST or somesuch did accelerated decay studies and fo

> the metallic mirror will oxidize after a few years and the disk will become impossible to read. I think NIST or somesuch did accelerated decay studies and found even moderately decent storage conditions for plain DVD-/+R was 30 years, with BD-R in the same conditions being vastly longer than that. I do know that i have 20+ year old CD-R backups* that still work, and as far as i can tell all of my DVD backups from 2002 and on still work. I recently got some 100GB BD-R but haven't written them yet, my laptop doesn't have enough storage for windows to do its thing, and i have 0 idea how to do a bd-r "files" backup on linux. Every google result is "how to back up your blu-ray movies" which is explicitly not what i want to do. * I also had a DVD-RAM drive in 1998/1999, with the "caddy" cartridge, and probably still have a couple of those discs, unsure if they work/if i can read them.

adrian_b 6y ago
It is true that there are optical discs that will survive for a long time, because the plastic coating of the metal has a low enough permeability to the oxygen from the air. The problem is that as an individual, it is impossible to guess whether the discs that you have bought are good and they will last 50 years or they are bad and they will last only 2 years. There have been many published cases when the lifetime claims made by manufacturers were proven to be false. The reason is that it is difficult to control the permeability of the coating during production. While many discs may be good enough, there are also many that will have a short lifetime. The risks of storing data on standard optical discs are too large to be acceptable. There were special archival-quality optical discs with gold reflective layers, e.g. made by Kodak. Those could really be guaranteed for 100 years or more, but they were too expensive, so they were discontinued.

adrian_b 6y ago

It is true that there are optical discs that will survive for a long time, because the plastic coating of the metal has a low enough permeability to the oxygen from the air. The problem is that as an individual, it is impossible to guess whether the discs that you have bought are good and they will last 50 years or they are bad and they will last only 2 years. There have been many published cases when the lifetime claims made by manufacturers were proven to be false. The reason is that it is difficult to control the permeability of the coating during production. While many discs may be good enough, there are also many that will have a short lifetime. The risks of storing data on standard optical discs are too large to be acceptable. There were special archival-quality optical discs with gold reflective layers, e.g. made by Kodak. Those could really be guaranteed for 100 years or more, but they were too expensive, so they were discontinued.