Q: How long can I use a backup tape?

A: With tape media, you typically don't know a tape is bad until it fails--at which point it's too late. This issue is usually addressed by taking tape media out of circulation after a certain amount of time and assuming it's unreliable even if it hasn't had any errors. This is its useful duty cycle.

I've found that linear tape technology (DLT-/ LTO-based) that's used daily is typically pulled out of circulation after a year. Helical-scan technology is more prone to wear and, therefore, is removed from circulation sooner--generally after three to six months (with the most extreme cases after only 10 to 12 passes).

Most backup products can enforce a tape duty cycle by attributing an expiration period to the media (this is different from the expiration period that defines how long to retain the data on the tape). For example, Symantec's Veritas NetBackup allows you to assign an expiration date to a tape, after which the tape becomes read-only until all data on it expires and the tape is no longer used.

--Ashley D'Costa, practice lead, Mainland Information Systems