Replacing Tapes with DVDs

In his August 15 post Rethinking backup, ZDNet‘s Paul Murphy suggests replacing standard tape drives with a combination of RAID array and DVD superdrive. “The cash savings are obvious but other things may be more important. For example, high quality DVDs outlast tapes, cost less, and require less storage space.”

It’s true, people talk a lot about the 30 year shelf life of tape, and DVDs, like CDs, are sometimes subject to “rot.” But if you’re actually using tapes instead of keeping them on shelves, they wear out very quickly, getting stretched, tangled, etc—just like audio cassette tapes.

To make the proposed solution really successful, however, a company would have to determine which data really needed backing up. A tape holds a lot more data than a DVD, even though going through multiple DVDs to recover data might be faster than going through a single tape. And no one seems to have found a way to automate what Murphy calls “Just the Facts, Ma’am” backup: “a super automated diff[erential backup] that stored just the changes in those files.”

Readers have written in with a number of suggestions, including Intelligent Disk Backup from Net Integration Technologies. Many object that without the software to sort and compact the data, the proposed solution isn’t really a solution.

The tone of the discussion starts to deteriorate after a while, but there is an important lesson in this. The easiest way to back up is sort of like the quickest way to move house: throw everything you have into boxes and put it on the truck. But that means you need a bigger truck–and maybe even a bigger house to move into. There’s a trade-off between the simplicity of backing up your whole drive and the storage space it takes to do that.

If you only have a handful of computers, you can probably get them all backed up onto one external drive, but then again, that depends on the computers. A handful of computers like mine would easily fit on one good-sized XHD. A handful of the Ur-Guru’s computers, on the other hand, need something more.

If you have storage space to spare, then you don’t have to worry about compressing or selecting the data you back up. If not, you need to determine priorities. Maybe all the data that really matters would fit on a single DVD.