Backup Strategies

August 2, 2007

In my line of buisness, I often have to install, setup, and maintain backup services for clients on a wide array of hardware and software. In today’s post, I’ll discuss the PROs/CONs of doing different types of backup strategies.

Daily Full-

Ok, Basically this backup strategy is nothing more than backing up all of your data on a daily basis. Depending on how long you want to keep your data around, you would need a very large number of tapes to pull this off effectively. However, for a 7 day data retention policy, you would need a total of 7 tapes that would rotate in during it’s day of the week.

PROs: Easy to setup, easy to troubleshoot, ensures that you always have the data that you need in one of your backup tapes.

CONs: Backup Time, more read/write time on tapes and drive, inefficient

Recommendation: Great for small businesses with single tape drives, however, requires user intervention on a daily basis to be effective.

Weekly Full / Daily Incremental-

This strategy in a nutshell requires you to do exactly what it says, backup your data in full on a weekly basis, then follow that with an incremental (data that has changed since the last full or incremental backup. This strategy allows you to backup the longest time taking portion of your backup on a day or weekend in which you are not pressed to get the data backup finished by a specific time. Depending on your specific storage needs, you can get an entire weeks backup on two tapes. One tape for your full backup, then another for your daily incremental backups. This can be crafted into a pretty good solution for archiving your data backups or keeping a specific retention policy.

PROs: Easy to setup, cheap (less tapes required), less time required to backup on daily incremental backups.

CONs: Restores require all previous incremental backups and last full backup, not having to change tapes everyday could make you lazy.

Recommendations: This backup (in my opinion) is great for just about any size of network or business. The best thing about going this route is you can have as little as one tape or as many as your little heart desires (as long as your data fits).

Weekly Full / Daily Differential-

This method is pretty much the same as the previous except the main difference between incremental and differential backups. In a differential setup, you have your full backup, then a backup of everything that has changed since your last full backup. This is different than an incremental because, for example: full backup on Saturday/Sunday then daily differential backups throughout the week. On Monday, the backup would be exactly the same as in the incremental but on Tuesday, the backup would include everything that changed on Monday and Tuesday since your last full backup on Saturday/Sunday. This trend continues throughout the week which yes, does increase the size of your backups throughout the week but your restore only requires the full and the differential that has the version of file that you would like to restore. The backup retention policy is just as easy to setup and follow as the incremental setup.

PROs: Easy to setup, requires less tapes that daily fulls, faster than daily fulls, easy to recover data.

CONs: Recovery is still not as quick as a daily full.

Recommendations: I actually prefer this backup method over the previous two because you get all the benefits of of a full backup (well most of them) and really none of the downfalls.

Disk to Disk to Tape-

For the seriously large networks or just big backups this solution has a lot of value in it. What this allows you to do is have more read/write time on your tape backups. For example: do your initial backup utilizing any of the three backup strategies mentioned before but instead of writing to tape write to another drive array, then when that backup is finished you have the next 24 hours to complete your backup to tape cycle. Now obviously you would need a very large amount of data to get the full benefits out of this as it will be a little more expensive due to the extra space needed.

PROs: Allows for plenty of time to backup any amount of data, ensures that you have at least the last days backup on disk for quick and easy recovery.

CONs: Greatly increases cost (extra large drive array needed for disk backup), increases complexity of backup and recovery solution, in most cases requires extra licensing through backup vendor.

Recommendation: This last backup strategy is really my top choice but because of its CONs, namely the cost, this way is usually out of the question. However, I would recommend that you at least consider this plan if you are backing up more data that your current tape system allows you to backup in a specific amount of time.

I hope you read this and take something from it that may be of value, at least consider the possibility that your current solution is not perfect and look for ways to improve it.

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