Your homemade DVDs are toast

You thought you were doing the right thing by backing up your data to optical discs, since you know that all hard drives are prone to eventually crashing, wiping out everything with them.

Alas, even tech pros learn a hard lesson once in awhile: The New York Times' David Pogue blogged today that his homemade DVDs, videos burned to DVD-R using his Mac, are dying after just four years on the shelf.

In Pogue's sudden discovery, readability was dependent on the newness of the machine: One computer couldn't read most of the discs, one could read about half, and the final machine was finally able to read them all. But for how long? (Some drives are better able to handle errors, so if you find one of your discs not working, it's worthwhile to try another computer -- preferably a newer one.)

What happened? As Pogue notes, burnable DVDs -- as opposed to store-bought, pre-recorded DVDs -- use organic dyes in the read/write layer sandwiched between the plastic, and those dyes can break down over time (a condition with the affectionate name of "CD rot"). Conditions like excessive heat and light can exacerbate the problem, but all discs are susceptible. Conventional wisdom has held that home-burned discs should be able to last for 50 or even 100 years, but the pitiful four years that Pogue's discs barely survived should stand as a serious wake-up call to anyone using optical media for long-term archiving.

Pogue's ultimate solution is essentially the right one: He's now copying all the videos onto a giant, inexpensive hard drive. But he'll need two copies if he wants to be certain not to risk losing his videos again.

My strategy (as I've mentioned before) is to keep two copies on hard drives of computers in day-to-day use, constantly mirrored with each other. I periodically make backups to a third hard drive, which is unplugged and kept turned off except for when it's actively being used to copy files for backup. And finally, critical files (and anything under 2-3MB in size) are backed up to an online storage service to guard against a worst-case scenario.