Anecdotal evidence, but I've recently gone through my ancient CD collection (in so doing, I found Ubuntu 6.04 installers, AOL dial-up CDs and other relics) and archived them with GNU DDrescue. It had no problem reading all bar a handful of CDs from the mid-to-late 90s and early 00's - the failure rate was much lower than I expected. The failures were mostly completely visually identifiable too - the layers had started to separate.
I've also been backing up personal photos to DVD annually for quite a few years. Each disc contains encrypted Duplicity files, and a PAR2 archive to assist with any deep failures of the on-medium parity. I also usually include a disk or two of pure parity archives, to handle a total failure of any disk or two in the middle.
Each year I check the price of DVD vs. Blu-ray and when factoring in the cost of the burner DVD seems to stay just on top for $/GB. It doesn't help that I've still got spare DVDs lying around, and people basically give away the blanks these days.
This is not my only backup strategy, but it is the only one that is cold, read-only, and offline.
I've also been backing up personal photos to DVD annually for quite a few years. Each disc contains encrypted Duplicity files, and a PAR2 archive to assist with any deep failures of the on-medium parity. I also usually include a disk or two of pure parity archives, to handle a total failure of any disk or two in the middle.
Each year I check the price of DVD vs. Blu-ray and when factoring in the cost of the burner DVD seems to stay just on top for $/GB. It doesn't help that I've still got spare DVDs lying around, and people basically give away the blanks these days.
This is not my only backup strategy, but it is the only one that is cold, read-only, and offline.