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On 5/2/10 3:12 PM, "Bob Friesenhahn" <bfriesen@xxxxxxxxxxxxxxxxxxx> wrote:
> On the flip-side, using 'zfs scrub' puts more stress on the system
> which may make it more likely to fail. It increases load on the power
> supplies, CPUs, interfaces, and disks. A system which might work fine
> under normal load may be stressed and misbehave under scrub. Using
> scrub on a weak system could actually increase the chance of data
> loss.
If my system is going to fail under the stress of a scrub, it's going to
fail under the stress of a resilver. From my perspective, I'm not as scared
of data corruption as I am of data corruption *that I don't know about.* I
only keep backups for a finite amount of time. If I scrub every week, and my
zpool dies during a scrub, then I know it's time to pull out last week's
backup, where I know (thanks to scrubbing) the data was not corrupt. I've
lived the experience where a user comes to me because he tried to open a
seven-year-old file and it was corrupt. Not a blankety-blank thing I could
do, because we only retain backup tapes for four years and the four-year-old
tape had a backup of the file post-corruption.
Data loss may be unavoidable, but that's why we keep backups. It's the
invisible data loss that makes life suboptimal.
--
Dave Pooser, ACSA
Manager of Information Services
Alford Media http://www.alfordmedia.com
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