Comment by Const-me
3 years ago
CD-R drives were already common in 2001: https://en.wikipedia.org/wiki/CD-R
I wonder would a CD-R disk retain data for these 22 years?
3 years ago
CD-R drives were already common in 2001: https://en.wikipedia.org/wiki/CD-R
I wonder would a CD-R disk retain data for these 22 years?
Only if you kept the disk in a refrigerator. Bits are stored by melting the plastic slightly and the dye seeping in. Over time, the warmth of "room temperature" will cause the pits to become less well-defined so the decoder has to spend more time calculating "well, is that really a 1 or is it a sloppy 0". There's a lot of error detection/correction built into the CD specs, but eventually, there will be more error than can be corrected for. If you've ever heard the term "annealing" when used in machine learning, this is equivalent.
Living in South Florida, ambient temperatures were enough to erase CD-Rs - typically in less than a year. I quickly started buying the much more expensive "archival" discs, but that wasn't enough. One fascinating "garage band" sold their music on CD-Rs and all of my discs died (it was a surfer band from Alabama).
The recording is made in the dye layer, a chemical change, and the dye degrades (particularly in sunlight) so the discs have a limited shelf life. Checking Wikipedia, it appears azo dye formulations can be good for tens of years.
Melting polycarbonate would call for an absurdly powerful laser, a glacial pace, or both, and you wouldn't have to use dye at all. I'd guess such a scheme would be extremely durable, though.
I tried a couple of CD-Rs that were stored in a dry closed drawer for most of the last 20 years recently, and they seemed to at least initially come up. Now I can reinstall Windows 2000 with Service Pack 4 slipstreamed!