Check your backups
August 15, 2005
Backups have been in the geek news recently, courtesy of the chilling tale of the online comic Penny Arcade's backup failure. Making backups is important, but there's an equally important and far less appreciated piece: checking your backups to make sure that you can actually restore them.
You may say 'but, I'm sure my system would scream a lot if something was wrong'. Let me tell you a story about that.
Once upon a time there was a young and innocent system administrator. He had an Ultrix MIPS DECStation to take care of (which says something about how long ago this was), and part of taking care of it was backing it up. Dutifully he arranged tape backups; because he worked at a university, they were tape backups over the network to a remote tape drive.
Unfortunately the Ultrix backup program insisted on logging in to the
tape server as the wrong user (and which user it used was
hard-coded). No problem; this was a university, so he had full Ultrix
source code. Changing which user
While doing this, he noticed that
About a year later he accidentally did something to a relatively
unimportant file and decided he wanted to restore it from a backup. He
queued up the right tape, got the
I will cut to the punchline: the MIPS compiler had an optimizer
A year's worth of backups were literally worthless. The young system
administrator had a small heart attack, thanked his lucky stars he had
found this before he needed to restore anything important, recompiled
So, having stubbed my toe, I strongly urge you: test your backups by trying to restore at least something from them. If you don't, you don't actually know if you have backups, you just think you do. (And remember, 'optimisim is not a plan'.)
Written on 15 August 2005.
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