A tape rotation method is a procedure that specifies when each particular tape will be used, and what will be backed up to it. For example, for a simple tape rotation scheme, you might label five tapes Monday through Friday and then do a complete full backup to the corresponding tape each day. Some tape rotation methods are simple and use only a few tapes. Others are immensely complex and use many tapes. Choosing the most appropriate tape rotation method is a critical step in developing and implementing your backup plan.
On one extreme, you could use the same tape everyday, but that has obvious dangers, including the risk of that one tape being lost or damaged, the inability to retrieve a file that was deleted or corrupted more than a day previous, and the inability to keep an offsite copy. On the other extreme, Robert once did some consulting for a law firm that never reuses a backup tape. Every evening they do a complete backup and compare of their “active” volumes to a new tape, which is then stored indefinitely in their vault. They regard the small daily cost of a new backup tape as trivial relative to the benefit of being able to reconstruct their data exactly for any specified day.
Chances are, the best tape rotation method for you falls somewhere between those extremes. Here are some issues to think about when you choose a tape rotation method:
When you need to do a restore, whether of a single file accidentally deleted or of an ...