Every now and then, I attend a conference and run across some news I can use. Often, as today, passing reference to the theme emerged in sessions that my table-mates then pick up on at lunch. Today’s dining chat centered on the operational life of technologies we use to store our growing libraries of digital photos and videos. The bottom line: Don’t store files on DVDs, I learned, unless you’re prepared to dump the disks every three months and create new ones from your original source files.

CDs will store your digital pix longer — maybe a year.

Your computer’s hard drive: That’s the safest place to store digital files that matter. There the bits and bytes that define a snapshot of Mt. Everest, your baby at 6 hours of age, or grandpa's prize-winning radish may survive unscathed for three years or more. I picked up these depressing tidbits from David C. Tarrant of the School of Electronics and Computer Science at the University of Southampton, England.

Now, I’m quite sure there are cadres of digital mavens for whom this is old, old hat. Certainly, the other guys at my lunch table — all attendees, here in Pittsburgh, of the Joint Conference on Digital Libraries — nodded in seemingly knowing agreement as Tarrant dispensed his pearls. But me, I was actually shocked to hear how unstable they find our new media.

I know what you’re probably thinking. That music CD of ABBA’s later hits, purchased when the Swedes were winding up their active period in the early ‘80s, still plays on the rare occasion you take it out for a trip down nostalgia lane. But that’s because manufacturers do a better job, as a rule, of protecting their files on commercially recorded, play-only CDs, Tarrant explains. The download-it-yourself CDs are another story, he says. And the record-it-yourself DVDs, they can start degrading substantially within a year.

So where do people like Tarrant, who investigates ways to preserve digital repositories of potentially invaluable files — such as research data — recommend keeping family pix or other digital memorabilia that we hope to save for all eternity? CDs are fine, he says. Just keep backing them up every year. And “migrate” the original files from your old hard drive to a brand new hard drive every two to four years.

Of course, Tarrant seems like a stickler for authenticity, that is, keeping data from any unintended alteration. Most of us can probably live with the loss of a few bytes here or there. Maybe it will alter a color somewhat or give us a microhole — absence of data — in the winter coat Aunt Sarah was wearing the last time we took her snapshot. But expecting all of our libraries of photos to sleep safely within those CDs on the shelf: That’s apparently folly.

It also argues against putting them in a time capsule. Even without using them, they’ll just degrade before the next generation retrieves them. Much like those old mid-century photographic slides did that dad saved on the closet shelf.

I just wish that all of those people who have been pushing digital cameras on us for the past decade, hawking them as “better than film,” had warned us that their products would be so ephemeral.

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