Takeaway: Consultant Peter Herbener has compiled a series of disaster recovery worst practices based on his experience. Trying to save money on backup media often backfires. If you're struggling with the basics, here are some tips to get back on track.
You can back up your computer to any of several types of media. You can use tapes, some sort of writable CD or DVD, flash drives, or external hard drives. You can even back up to the hard drive of another computer over a LAN or the Internet. In the "olden" days, people even used diskettes.
Whatever media you use, most people reuse them. Instead of using a brand new tape every time, people will take a tape they've already used to make backups and use it again for today's backup. There's nothing wrong with that, especially since one tape can cost $40 to $80. Expensive tapes might tempt some people to just buy one tape and use it again and again every day.
DR worst practices
Nightmare: Not enough backup tapesI once knew someone who knew that her computer's hard drive was likely to fail at any time. There had been some error messages and funny noises, but she was able to coax it to keep working. Since she knew it was a matter of time before that drive quit for good, she was very careful to back up her data every day. This was several years ago, so she was using diskettes. The backup program would fill up a diskette, and tell her when to put in another so it could continue. This took 12 diskettes.
One day when backing up, she got to the eighth diskette when she received the dreaded error message informing her that the file being backed up couldn't be read. The hard drive failed right in the middle of doing the backup.
Here's the sad part. She had only one set of 12 diskettes that she reused every day. As soon as she started backing up, the backup program wiped out her previous day's backups from the disks. So she didn't have yesterday's backup anymore.
However, she hadn't finished today's backup, so she didn't have that one either. For the half hour or so that it took to do a backup, she didn't have any backup at all. And that's when she found out that she needed the backup!
If you think about it, she should have saved herself the trouble and not bothered with doing any backups. Having only one backup tape isn't much better than not having any at all.
Slightly better practices
Variation 1: Okay, I'll have two and rotate between them.
This sounds a little better. If you rotate between two tapes and you run into a problem like the one above, you've always got an extra. I still think that's too risky, though. It seems that when something bad happens, it's unlikely that everything else will go smoothly.
If you have only one backup tape and it's GOT to work, that's when the tape will break or something else will go wrong. If you're rotating tapes, having less than three is tempting fate. Sometimes that's not enough.
Variation 2: It worked fine the last time I used it (three months ago).
Most people have several sets of media and rotate them. But how many sets of media do you need? Here's another classic mistake:
A small retailer used his computer to track daily sales and expenses and to prepare quarterly and annual taxes. He felt it wouldn't be terribly difficult to reconstruct a couple days of activity, so he decided to back up only on a weekly basis.
Each backup took one tape. To make it simple, he had four tapes. He labeled his tapes "Week 1," "Week 2," "Week 3," and "Week 4." As you might guess, on the Friday of the first week of the month, he backed up to the "Week 1" tape. The next Friday he would use the "Week 2" tape, and so on. The next month, he pulled out the old "Week 1" tape and reused it.
This sounds like a good plan except for one thing. He usually only used his tax program once every quarter. One quarter, he tried to open up his tax program, but it couldn't pull up his data. Somehow, something had damaged his data files.
Not a problem, he thought, and restored from his most recent backup. That didn't work either. He restored one tape after another, but still didn't have any luck. His oldest backup was a month old, but the damage happened before that. However, since he hadn't used that program in three months, he had no idea there was a problem.
On the basis of that problem, he added more tapes. These are labeled for each month (January, February, etc.), and on the first Friday of each month, he uses the corresponding monthly tape instead of the "Week 1" tape. Then he puts it aside and it doesn't get reused for a whole year. The rest of the month he continues with his weekly tapes.
Why not just make a special backup every quarter? First, it's harder to keep track of "special" backups. Next, monthly backups give you lots more options. You might find you need to go back two months or four months to find an important piece of data. Finally, remember that when problems strike, other things don't always go smoothly -- you might run into problems with that lone tape.
How many times can I safely reuse a tape?
Check with the manufacturer to see how many times a tape can be reused. The specifications for some tapes claim "100,000 passes," but a single use might involve several passes. Even so, that's a long time.
While it's possible to wear out a tape, most small operations need to worry much more about accidentally damaging their tapes. The worst things to do to tapes are to drop them or leave them in places that are too hot, too cold, or too humid.
Larger IT shops might need to worry about retiring tapes that have been reused too many times. However, a tape aging and wearing out from normal use is not worth worrying about. (You'll probably need a larger or faster tape drive before that happens!)
Best practices for backup media
Have several backup sets.
Reusing your backup media is okay as long as you do it right. If you rotate your tapes (or flash drives or whatever), make sure you have at least three backup sets -- and probably more. Having only one is about as good as having none at all.
Have some old backup sets.
Many problems won't appear for some time. For example, suppose you accidentally deleted a file three months ago, but you didn't need it again until now. It will help to have at least a couple of older backups, in case this happens.
Don't damage your tapes in storage.
You'll probably never wear out a tape with normal use, but you can damage it. First, don't drop the tapes. Next, avoid letting them get hot or cold. Don't leave them in a car, especially during extreme weather.
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