CD-R life expectancy

Just read a post over at The Register that had me scrambling for more info about archival stability of CD data backups. The post cites an article in a Dutch computing magazine which reported some rather shocking rates of data corruption in stored disks after only 20 months.

However, no reason to panic quite yet. While The Register concludes that the Dutch testing "seems to suggest that CD-R is the wrong medium to store photos, music or data files for posterity", it also notes, crucially, that "the article seems to focus on white label CD-Rs, and doesn't mention any premium brands that performed well."

Considering that the premium brands continue to present their disks as good for many years (and even decades), I'm sure we would have heard more were there a real problem with data loss. In any case, my online digging suggests that the best archival CD-R disks use gold and phthalocyanine dye. Kodak used to make such disks, but Mitsui now seems to be the only source. Their best disks are rated for over 100 years, but are not widely stocked. Price would seem to be the reason, but at around $1.30 per disk they are cheap enough that I will be ordering some for my own important backups [I've now found their second-best gold disks at well under $1 -- D.].

Mitsui's own tests suggest that most of us need be less concerned with the metal coating (gold vs silver) than with the dye. Their silver-coated disks are rated for 50 years, and cost only a bit over 50 cents each. I'm still sitting on quite a few off-brand disks harvested for next to nothing during various rebate offers, but it now seems prudent to use them up for tasks such as weekly backups and sending family pictures to relatives.

Though I suppose rendering old disks unreadable is pretty trivial (scratching up the top, unshiny side, and breaking the disk to pieces will do nicely), it is interesting to read that simply leaving CD-Rs out in full sun for a few days will break down most disks' dye layers.

UPDATE: I should note that all of this applies equally to DVDs. Interestingly, Mitsui Chemical's former optical storage media division is currently US-based (main manufacturing site in Colorado, secondary in France), with majority ownership by an Italian holding company. Their website now barely mentions the Mitsui name, MAM-A being the new monicker.

FURTHER UPDATE (July 2006): Whoever makes them now, one can still get Kodak Preservation Discs through any number of specialist retailers; Mitsui/MAM discs are remain widely available, and it pays to search under both names.

Posted by David on September 2, 2003 2:24 PM