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List:       opensolaris-help
Subject:    Re: [osol-help] repair pool - Permanent errors
From:       Edward Ned Harvey <opensolarisisdeadlongliveopensolaris () nedharvey ! com>
Date:       2011-04-20 12:45:29
Message-ID: 000001cbff58$d7d3ad90$877b08b0$ () nedharvey ! com
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> From: opensolaris-help-bounces@opensolaris.org [mailto:opensolaris-help-
> bounces@opensolaris.org] On Behalf Of Andre Lue
> 
> Try a zpool scrub. Be prepared to be real patient. It could take a while
for the
> scrub to complete. Do not power cycle the machine to break the sequence
> once started. It will most likely lead to more complicated issues.

The only thing a scrub can do in this situation, is to possibly find more
errors.  It can't correct the existing known error.  

When you scrub, it's going to examine every used block on every disk, and
verify its checksum.  If there is a cksum mismatch on any device, it will
attempt to correct it using good data from a redundant copy (the other side
of the mirror.)  If there is no good copy of the data found, then it results
in a permanent error.  The only thing you can do is to rm the file, and hope
you can find a good copy somewhere in backups.

In fact, anytime you use the filesystem for normal day-to-day reads and so
on, it is always checking the cksum for any block it reads.  And if a cksum
mismatch is detected, the behavior is as described.  When you scrub, all it
does, is to systematically read every block on every device, thus finding
all corruption and correcting all correctable corruption.

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