Messages in this thread | | | Date | Thu, 26 Apr 2007 22:21:02 -0700 | From | Valerie Henson <> | Subject | Re: ZFS with Linux: An Open Plea |
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On Wed, Apr 18, 2007 at 01:25:19PM -0400, Lennart Sorensen wrote: > > Does it matter that google's recent report on disk failures indicated > that SMART never predicted anything useful as far as they could tell? > Certainly none of my drive failures ever had SMART make any kind of > indication that anything was wrong.
I saw that talk, and that's not what I got out of it. They found that SMART error reports _did_ correlate with drive failure. See page 8 of:
http://www.usenix.org/events/fast07/tech/full_papers/pinheiro/pinheiro.pdf
(If you're not a USENIX member, you may be able to find a free download copy elsewhere.)
However, they found that the correlation was not strong enough to make it economically feasible to replace disks reporting SMART failures, since something like 70% of disks were still working a year after the first failure report. Also, they found that some disks failed without any SMART error reports.
Now, Google keeps multiple copies (3 in GoogleFS, last I heard) of data, so for them, "economically feasible" means something different than for my personal laptop hard drive. I have twice had my laptop hard drive start spitting SMART errors and then die within a week. It is economically quite sensible for me to replace my laptop drive once it has an error, since I don't carry around 3 laptops everywhere I go.
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