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What to do when a raid device has a mismatch count


== Contact Information ==
This SOP has moved to the fedora Infrastructure SOP git repo. Please see the current document at: http://infrastructure.fedoraproject.org/infra/docs/infra-raidmismatch.txt
Owner: Fedora Infrastructure Team


Contact: #fedora-admin, sysadmin-main
For changes, questions or comments, please contact anyone in the Fedora Infrastructure team.


Location: All
Servers: Physical hosts
Purpose: Provides database connection to many of our apps.
== Description ==
In some situations a raid device may indicate there is a count mismatch as listed in:
<pre>
/sys/block/mdX/md/mismatch_cnt
</pre>
Anything other than 0 is considered not good.  Though if the number is low it's probably nothing to worry about.  To correct this situation try the directions below
== Correction ==
More than anything these steps are to A) Verify there is no problem and B) make the error go away.  If step 1 and step 2 don't correct the problems, <b>PROCEED WITH CAUTION</b>.  The steps below, however, should be relatively safe.
=== Step 1 ===
Issue a repair (replace mdX with the questionable raid device):
<pre>
echo repair > /sys/block/mdX/md/sync_action
</pre>
Depending on the size of the array and disk speed this can take a while.  Watch the progress with:
<pre>
cat /proc/mdstat
</pre>
Once that's done proceed to Step 2.
=== Step 2 ===
Issue a check.  It's this check that will reset the mismatch count if there are no problems.  Again replace mdX with your actual raid device.
<pre>
echo check > /sys/block/mdX/md/sync_action
</pre>
Just as before, you can watch the progress with:
<pre>
cat /proc/mdstat
</pre>


[[Category:Infrastructure SOPs]]
[[Category:Infrastructure SOPs]]

Revision as of 18:19, 19 December 2011

Shortcut:
ISOP:mismatch_cnt


This SOP has moved to the fedora Infrastructure SOP git repo. Please see the current document at: http://infrastructure.fedoraproject.org/infra/docs/infra-raidmismatch.txt

For changes, questions or comments, please contact anyone in the Fedora Infrastructure team.

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