GFS Backups Explained

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Grandfather-father-son backup schemeAre you afraid of deleting old backups?  I am.  What if there’s something important in them, like files I deleted and didn’t realize I needed until months later?

Unfortunately, if you’re backing up regularly you’re going to run out of space eventually.  At that point, you can either buy more space (more tapes, a new hard drive, etc.) or start deleting your old backups.

There is a solution, however.

It’s called GFS: Grandfather-father-son, a backup rotation scheme.  The basic method is to define 3 backup sets, such as daily, weekly, and monthly.  You could also choose daily, monthly, and yearly, if you really want to keep backups a long time.

Does it really make sense to keep 180 days worth of daily backups?  Or would it make better sense to keep:

  • 6 daily backups
  • 4 weekly backups
  • 12 monthly backups

That’s only 22 backups, yet it covers an entire year whereas our 180 daily backups only covers half a year.  Pretty neat, huh?  That’s GFS in a nutshell.

To use GFS with tape-based backup systems, simply rotate each of your daily, weekly, and monthly tapes according to their cycle.  On the 7th day, the daily (son) graduates to a weekly backup (father).  On the 4th week, the weekly backup graduates to a monthly (grandfather).  The daily and weekly tapes get re-used during the cycle, while the monthly tapes are removed from the cycle and usually stored securely offsite.

What if I backup to a hard drive?

A GFS rotation scheme can be done in most modern-day backup software.

Create 3 separate jobs: one for daily, weekly, and monthly backups.  Perform daily backups 6 days a week.  On the 7th day, create a weekly backup.  On the last day of the month, perform a monthly backup.  Have the software keep no more than 6 versions of daily backups, keep 4 versions of weekly backups, and keep monthly backups as long as needed.

Geoff Akerlund

Geoff Akerlund

Geoff Akerlund is the founder and editor-in-chief of BackupReview.com. He enjoys attending music festivals, whitewater kayaking on the American River, and board game nights in his free time.

Geoff Akerlund

@backupsoftware