No discussion of tape as a backup solution would be complete without treating the subject of Tape Rotation, or, more generally, Backup Rotation. Plug either phrase into Google and you’ll get a vast collection of hits outlining different strategies based on how many tapes you use and how often you back up.
Why rotate tapes at all? Why not just rewind and tape over the previous backup? Well, as most of us know from experience, tapes wear out: there are only so many times you can record or play any given tape. This is also true, if less obviously, for rewritable CDs and DVDs, and even for floppies, ZIP disks, and hard drives. Rotating your backup media makes each individual tape or disk last longer—even if it is one of the reasons that tape backup is an expensive solution for a small or home office.
For people like me who are allergic to math, these rotation strategies are pretty confusing, though the principle is fairly simple: you start with a full backup and then make daily and/or weekly incremental backups (just the files that have changed) until it’s time for the next full backup. Depending on how many sets of tapes or CDs/DVDs you use, you’ll have backups that cover anything from a week to several months.
Why would you want so many copies? Isn’t the most recent backup enough?
Yes and no. If your files get lost or damaged, or your computer gets infected with a virus or swamped with spyware, your most recent backup might not do you much good. You’ll want a backup from a time before things went wrong. I keep the most recent three Ghost backups, labeled by date, as well as making daily backups of my files. That way, if I need an earlier before-I-messed-with-it version of a file, I can restore it from a previous week’s Ghost backup.
Tape rotation also allows you to keep all but the tape (or disk) that you’re using that day off-site, ensuring that you’ll never lose more than one day’s work.
Of course, you need to be using backup software that can recognize which files have been backed up, but that’s standard for tape-backup software and even included in the Microsoft Windows Backup Utility.
How many tapes or disks do you need for a backup rotation? The true geek’s answer to that question is “Just one more,” but the minimum is three and the maximum is 20. (For instructions on backup rotations using three, six, and ten tapes, see the Imation website.) Three tapes or disks are probably sufficient for most small businesses, but it depends on how valuable your data is to you—or how paranoid you are.
There are actually names for different methods of tape rotation: the Tower of Hanoi (5 tapes), Round Robin (5 tapes), and Grandfather, Father, Son (GFS for short; 20 tapes). If you like mathematical puzzles involving stacking rings on rods, you’ll enjoy these. If, like me, you fail miserably at such tests, you’re probably going to choose another backup option out of sheer confusion. You might even be inspired to pay a visit to the Tape Sucks website.
Exabyte does provide very detailed instructions for these methods in its Basic Backup Guide, but even they describe the Tower of Hanoi as “too complex to track tape rotation manually.” Heck, I could tell that just looking at the picture at ABC Technologies.
Rotating your backup media makes sense, but if you’re not using an automated system, stick to something simple. A backup routine which is too complex is a backup routine you won’t use, and having no backups is much riskier than wearing out a tape or CD by re-using it every day.
That about winds it up for tapes. Tune in next week for more backup news from The FileSlinger.