Unix Backup and Recovery

Testing Your Backups

I wish there were enough to say about this to make it a separate chapter, because it’s that important. I can’t tell you how many stories I have heard about people who wait until they need a major restore before they test their backups. That’s when they find out that they’ve been using the wrong device or the wrong blocking factor or that the device had I/O errors. This point cannot be stated strongly enough. If you don’t test your backups, then you are guaranteed to get a surprise sooner or later.

Test Everything!

It is important to test every type of restore. If you are testing filesystem backups, make sure you:

• Restore many single files. Can you find the needle in the haystack?

• Restore an older version of a file.

• Restore an entire filesystem, and compare your results with the original. Are they the same size, and so on?

• Pretend that an entire system is down, and try to re-create it.

• Pretend that a particular volume is bad, and force yourself to use an alternate backup.

• Retrieve a few volumes from your off-site storage vendor.

• Pretend that your backup server is destroyed, and try to recover from that. (This one’s tough!) This test is extremely important if you are using a commercial backup utility. Some products do not plan for this well, and you can find yourself in a real catch-22 situation.

If you are testing database restores, make sure you:

• Restore part of your database, pretending that you lost only one data file or disk drive, if this option is available.

• Restore ...