How GFS Rotations Work

The most commonly used media rotation schedule is the Grandfather-Father-Son (GFS) rotation. This schedule policy uses daily (Son), weekly (Father), and monthly (Grandfather) backup media sets (tapes). GFS rotation schedules allow you to back up your data for an entire year using a minimum of media (tapes). The number of tapes you use for GFS rotations is based on the number of workdays you specify for your backup policy.

The GFS rotation method works as follows:

Note: To avoid confusion, it is important to clearly and properly label your tapes.

• You back up your data on a separate tape every working day. You should use a different tape for every daily backup. For example, if your backup cycle is based on a five-day workweek, you will need four "Daily" tapes before you use a weekly tape. (Maybe label the daily tapes Monday, Tuesday, Wednesday, and Thursday or Daily 1 through Daily 4, and so on.). You can perform Full, Incremental, or Differential backups for your daily backups. After the fourth day, the first daily tape used is then re-cycled and can be overwritten with the next scheduled daily backup.
• Remember, because the daily tapes are used more frequently than the weekly and monthly tapes, you will need to replace them more often.
• On the fifth day, instead of using another daily tape, you will use a "Weekly" tape. You should always perform a Full backup for your weekly backups. You should also use five weekly tapes before you use a monthly tape. (Maybe label the weekly tapes Week 1 through Week 5). After the fifth week, the first weekly tape used is then re-cycled and can be overwritten with the next scheduled weekly backup.
• At the end of the third week, instead of using another weekly tape, you will use a "Monthly" tape. You should also perform a Full backup for your monthly backups. You should have 12 monthly tapes to safely backup a full year of data. (Maybe label the monthly tapes January through December or Month 1 through Month 12, etc.). After twelfth month, the first monthly tape used is then re-cycled and overwritten with the next monthly backup.

The following diagram shows an example of how a typical 5-day GFS rotation policy can be implemented to provide you with a safe and reliable method to perform data backups for an entire year while using a minimum amount of backup media:

Note: A five-day GFS rotation policy would require approximately 21 tapes per year, while a seven-day policy would require approximately 23 tapes per year (adding two additional daily tapes). For both of these schedules, the amount of media needed can vary depending upon your specified retention criteria and the quantity of data that you are backing up. Additionally, the amount of media needed in each schedule can also be affected by the use of multistreaming and if you are appending backup sessions to your media.