Quick primer on GFS backup rotations

by Ed Hagihara

At another company that I worked at, both myself and another administrator at another site had to manage our local site backups, rotate tapes, send them offsite, etc..  Well, one of them unfortunately didn't do so well in understanding how we managed our backups and apparently more than once messed up the rotations bad enough that certain critical backup jobs wouldn't run - and made the recovery of needed documents impossible.  So as a result, one of the directors of IT got fed up enough with this individual that he requested that we each write up a document outlining and describing our backup jobs and rotations to make sure that we could explain what we were doing.  The other person didn't last too much longer.  This was my quick rendition.

GFS Rotation schedule –  This document briefly outlines what is known as a GFS (grandfather – father - son) rotation which considered a common backup practice among many companies:

Example: February 2000 (note: daily tapes are in black, weekly tapes are in red, and monthly tapes are in blue.)

 Weeknights (also called daily tapes) – Company backup operators get an incremental or full backup (depending on backup), every Monday through Thursday ONLY (4 tapes for the daily tapes), which is retained for 2 weeks then goes back into the rotation.

If the job is a full backup, the tapes will be recycled on a daily basis every week. In this example, for instance, if I start a week cycle starting on the 7^th, I would ideally use one tape per day, Monday through Thursday, until the 10^th, THEN start recycling the tapes on the 14^th.

If the job consists of incremental backups, then the incrementals will run on Monday through Thursday, with a separate tape for the full weekly Friday backup.

Weekends (also called weeklies) - Company backup operators get a full backup every week on Friday (irrespective of whether or not it’s a full or an incremental backup), which then each weekly tape is then kept for 4 weeks, and recycled every month. These are named "weekly". In the example, the weeklies would be considered the 4^th, the 11^th, the 18^th, and the 25^th.

Monthly – Company backup operators get a full backup on the last day of every month. These tapes are kept for archival purposes and are NEVER to be recycled again. This way we have a way of having a sort of “snapshot” of information that we have had over the years. One caveat: If someone wants to retrieve something, for instance, 6 months ago, we do not have the ability to go back to a specific day to retrieve a piece of information unless the information was backed up at the end of the month (i.e., the 29^th) at some point.

Disaster Recovery – for best protection backup tapes should be rotated off-site regularly (either by a 3^rd party company or in another site location) in the event that a catastrophic event (such as earthquake or a war) occurs. If your business goes down, you want to ensure that there is a way to get critical data back quickly.