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Friday, September 15, 2006

Optimizing Your Backup Tape Rotation Strategy

Backups are a primordial part of any corporate disaster recovery plan, so to maximize their effectiveness you have to keep your data as long as you can, on the least number of medias possible. We don't want to have 600 tapes sitting uselessly in an expensive out-of-location vault when there's a way to only have a few. Backup tapes can be expensive and secure storage space is even more so.

There are many ways you can rotate your backup medias, but today I'm going to talk to you about my strategy of choice: the Grandfather-Father-Son (GFS) backup rotation strategy.

To use this rotation scheme you'll need:

  • 4 Daily or "Son" tapes (or 8 if you rotate these tapes bi-monthly)
  • 3 Weekly or "Father" tapes
  • 1 Monthly or "Grandfather" tape (Not reusable, you need a new one each month)

Here's a small graphic showing you my backup schedule:

(click to get a larger view)

You can see by looking at the graphic, the GFS method will allow you to go back to get data anywhere in the last 2 weeks, all end-of-weeks for a month, and all end-of-months for as long as you want to keep your monthly tapes.

All tapes, except the "Grandfather" one, will be reusable. The "Grandfather" tape is usually removed from the rotation scheme to be stored off-site on the last business day of each month. A new Grandfather tape has to take the place of the old one for the next monthly backup.

People who back up a huge amount of data usually do full backups on Weekly and Monthly tapes, and incremental ones for daily backups. Since my company doesn't have that much information to back up, I do full backups all the time. It's a matter of choice.

One of the disadvantages of using the GFS rotation scheme is that each tape is used until it fails, and tapes do fail, trust me. The only thing you can do to prevent this is to replace your most used ones once in a while. I replace my daily and weekly tapes every 2 years. Some manufacturers suggest that their media can support up to 10,000 cartridge uses, but I prefer not to take any chances.

As you can see, having a good rotation strategy for your tapes has many advantages. If you are not using such a strategy already, what are you waiting for?

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  • nice

    By Anonymous Anonymous, at 3:44 PM  

  • Ahhh GFS. Everyone hates backup solutions and their cost, until they have lost alot of really important data.

    Nice article.

    By Blogger Chief911, at 10:48 PM  

  • I believe people think about backups wrong way. As an IT consultant, clients always ask me for a backup solution. What they need is a restore solution.

    Ok, you do need to take a backup, but what you want to do is a restore!

    By Blogger A Paton, at 5:48 AM  

  • Just rotate a different Son tape to be the Grandfather each month. That way, your oldest tape (the Grandfather) is never more than 8 months old, and a fresh tape goes into the rotation every month.

    By Anonymous Anonymous, at 7:12 PM  

  • How about a tapeless system?

    I have DATA with this much DISK on N servers resulting in T "tapes":

    T = int ( DISK / DATA ) * N

    My grandfather is an archive to tape.

    In my case T is 6. I rsync my data to one of the "tapes" to do my backup.


    By Anonymous Anonymous, at 1:17 PM  

  • To the last commenter: the only problem with this is with storing your backups off-site..Unless you want to "rotate" external drives, which would turn your solution into an expensive one... and sending only 1 tape offsite per month clearly creates a dangerous situations.

    By Blogger Kiltak, at 1:32 PM  

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