Posey's Tips & Tricks

Top 3 Best Practices for Backup Testing

Backup testing is a critical IT process, but no one ever talks about how to do it properly. Here are Brien's best tips for testing your backups.

One of the first rules that IT pros learn -- but often ignore later on -- is the importance of testing their backups. Backup testing is one of those things that we probably all get sick of hearing about, but the topic keeps coming up because it is so important. After all, a backup is no good if you can't restore it. I once saw an organization lose the entire contents of its mail server because it had been performing backups incorrectly and didn't realize it until the day the backups were needed.

As important as backups might be, I rarely (if ever) hear anyone talk about how to properly test backups. As such, I wanted to pass along a few words of wisdom.

Before I get started, though, I need to point out that I am only going to address the topic at a relatively high level. The way that you need to test your backups is going to vary heavily depending on what you're backing up and what backup software you're using. Even so, there are a few things that are more or less consistent across the board.

Walk Through the Recovery Possibilities
One of the first bits of advice I want to pass along is that when you are testing your backups, it's important to try different types of recoveries. Suppose that you are backing up a mail server. You might try recovering an individual e-mail message, an entire mailbox, the entire mailbox database, the mail server application and the server as a whole. Remember, you never know what type of problem might force you to restore a backup, and it's important to be able to align your restoration efforts with the problem at hand. You wouldn't, for example, want to restore an entire mailbox database just to get one mailbox back.

My point is, regardless of what workload you're protecting, you should think about all of the different types of restorations that you may have to perform, and make sure that you are able to perform those types of restore operations.

Will the Backup Be Usable?
Another thing to consider: Verifying that you are able to restore a backup isn't necessarily the same thing as making sure the backup works. Imagine that someone accidentally deleted a couple of operating system files from one of your servers, but nobody realizes the files are gone. Just to make things interesting, let's also assume that these files are only used during the boot process. In other words, the server is going to keep working until it is rebooted. Now, suppose that someone reboots a server and, of course, it fails to boot correctly. Rather than attempting to manually correct the problem, someone decides to restore a backup.

The problem with this approach is that the backup may or may not contain the missing system files depending on when the backup was created. In other words, you may find that you are able to restore the backup but the backup is unable to return the system to a functional state because key system files are missing.

This is why I said that being able to restore a backup isn't the same as making sure the backup works. In this example, the backup restored just fine, but it failed to do what the organization needed it to do. The lesson is to not just verify that you can restore a backup, but also to make sure that the operating system, application and everything else is functional on the restored system.

Test Restoring to Dissimilar Hardware
One more thing I want to mention is the importance of verifying that you can restore a backup to dissimilar hardware. Obviously, most systems these days are virtual, making hardware mostly a nonissue. Even so, there is one thing in particular that you need to be on the lookout for: A lot of backup applications have trouble restoring a volume to a disk (physical or virtual) that is of a different size than the one that originally accommodated the volume. It's usually possible to work around this issue, but it may require you to jump through a few hoops depending on what backup software you're using.

That being the case, I recommend trying to restore a volume to a differently sized disk just to see what will happen. Hopefully, the process will be completely seamless. If it doesn't go smoothly, though, the testing process will help you figure out what you need to do to work around the issue before you ever encounter the situation in the real world.

About the Author

Brien Posey is a 19-time Microsoft MVP with decades of IT experience. As a freelance writer, Posey has written thousands of articles and contributed to several dozen books on a wide variety of IT topics. Prior to going freelance, Posey was a CIO for a national chain of hospitals and health care facilities. He has also served as a network administrator for some of the country's largest insurance companies and for the Department of Defense at Fort Knox. In addition to his continued work in IT, Posey has spent the last several years actively training as a commercial scientist-astronaut candidate in preparation to fly on a mission to study polar mesospheric clouds from space. You can follow his spaceflight training on his Web site.

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