On Wed, 11 Jun 2014, Bart Kus wrote:
Doing the periodic check does not prevent corruption of read() data though
(RAID6 case). Copied files may be corrupted, even though the RAID would
eventually fix itself after a repair is done.
Yes, there is a performance penalty, but data integrity is also improved.
Paranoid mode should probably not be the default, but I would like the choice
to improve data integrity at the expense of some small speed penalty. ZFS
implements this anti-corruption checking by using checksums on their data.
We don't have a simple checksumming mechanism in md-raid, but we do have the
full stripe data available ready for verification.
BTW, the idea of a daily repair operation doesn't work when it takes 14 hours
to repair a large RAID. That would only leave 10 hours of each day for
normal speed access. I schedule repairs weekly, though.
Since bytes read and written is the dominating factor behind disk failures
these days, I certainly wouldn't want to do repairs daily. Weekly might
even be pushing it.
/Mattias Wadenstein
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