Tape Rotations

After you have decided on the backup type you will use, you are ready to choose a backup rotation. Several backup rotation strategies are in usesome good, some bad, and some really bad. The most common, and perhaps the best, rotation strategy is the Grandfather, Father, Son rotation (GFS).

The GFS backup rotation is the most widely used and for good reason. An example GFS rotation may require 12 tapes: four tapes for daily backups (son), five tapes for weekly backups (father), and three tapes for monthly backups (grandfather).

Using this rotation schedule, it is possible to recover data from days, weeks, or months previous. Some network administrators choose to add tapes to the monthly rotation to be able to retrieve data even further back, sometimes up to a year. In most organizations, however, data that is a week old is out of date, let alone six months or a year.

Backup Best Practices

Many details go into making a backup strategy a success. The following list contains issues to consider as part of your backup plan.

  • Offsite storage Consider having backup tapes stored offsite so that in the event of a disaster in a building, a current set of tapes is still available offsite. The offsite tapes should be as current as any onsite and should be secure.

  • Label tapes The goal is to restore the data as quickly as possible, and trying to find the tape you need can be difficult if not marked. Further, it can prevent you from recording over a tape you need.

  • New tapes Like old cassette tapes, the tape cartridges used for the backups wear out over time. One strategy used to prevent this from becoming a problem is to introduce new tapes periodically into the rotation schedule.

  • Verify backups Never assume that the backup was successful. Seasoned administrators know that checking backup logs and performing periodic test restores are parts of the backup process.

  • Cleaning From time to time, it is necessary to clean the tape drive. If the inside gets dirty, backups can fail.