On 03/04/2011 12:30, Jonathan Tripathy wrote:
This is what state my server is currently in:
State : clean, resyncing
With mdadm 3.2.1, this will show "checking" when it is checking,
rather than "resyncing".
Interesting. So during a normal "resync", I'm guessing redundancy will
be lost?
You only need a resync when you've already lost redundancy. The only
normal resync is at array creation time, when mdadm will instantly
create the array with no redundancy and then proceed to generate the
mirror/parity information. Any other resync is only required after
something else caused a loss of redundancy e.g. a disc dying or a system
crash, or perhaps a drive threw up a bad sector. The check process will
attempt to discover any such problems.
As Doug Ledford noted in the Red Hat Bugzilla there are times when a md
RAID 1 can harmlessly end up out of sync.
Also, if the "checking" process finds an error, where will I
find it? /var/log/messages?
In the email the raid-check process sends you. Any errors found are not
reported in detail on RHEL/CentOS 5 - I think more recent kernel/mdadm
can be asked to be more verbose about the location of errors. Requesting
a repair rather than a check would get the check process to
automatically resync any stripes which had bad mirrors/parity.
In short, it is safe to ignore a modest mismatch_cnt on RAID 1 as long
as you aren't seeing disc errors, and that is what Doug Ledford's patch
to raid-check does.
Cheers,
John.
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