Causes of Hard Drive Failures

An article in the Proceedings of the 5th USENIX Conference on File and

Storage Technologies this month offers perhaps the most in-depth study

of hard drive failures to date. Google uses hundreds of thousands of

hard drives to store its data, and a sample of one hundred thousand of

Google's drives was studied for five years to determine common causes of

failure. Since this very interesting article is a little dense to read

in its entirety, I thought you would enjoy reading some highlights.

Going against conventional thought, the study determined that increased

temperature and/or activity had little or no correlation to failure

rate. By extension, it was found that drives spinning up and spinning

down most often had the highest failure rates. This means it's best to

uncheck the "Put the hard disk(s) to sleep when possible" box in Energy

Saver — at least in terms of hard drive health. Some SMART (self

monitoring and reporting technology) parameters are excellent indicators

of impending mechanical failure. Among failed drives, a good chunk gave

no warning by SMART, even though SMART- monitored parameters were to

blame for failure. For this reason, SMART is most useful as a

statistical predictor of failure for a population of drives rather than

on individual devices. With that in mind, if your drive reports SMART

errors you should at the very least immediately perform a full backup.

About 3% of drives failed in the first three months, 1.8% in the first 6

months, 1.7% in the first year. From there, failure rates jump to

approximately 8% in the second year, 9% in the third year, fall to 6% in

the fourth year, and jump back to 7% in the fifth year. The whole

article can be read at: <http://labs.google.com/papers/

disk_failures.pdf> ~ Matt Klein Small Dog Electronics

Andrew Webb

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blogging just like everyone else at

www.informationcontraband.com

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