[CentOS] mismatch_cnt after 5.3 -> 5.4 upgrade

Ryan Wagoner rswagoner at gmail.com
Mon Oct 26 16:51:27 UTC 2009


The /etc/cron.weekly/99-raid-check script is new for 5.4. Read through
the mdadm list. You will find that small mismatch counts on RAID 1 is
normal. I don't remember the exact reason but it has to do with
aborted writes where the queue has already committed the one drive and
not the other. Since it is in an unused area of the file system and
mdadm can't tell when the aborted write happened it is just left
alone. This is why it is common on swap partitions.

Ryan

On Mon, Oct 26, 2009 at 2:48 AM, Mogens Kjaer <mk at crc.dk> wrote:
> On 10/25/2009 07:33 PM, Devin Reade wrote:
> ...
>>         WARNING: mismatch_cnt is not 0 on /dev/md0
>
> I have two machines with software RAID 1 running CentOS,
> they both gave this message this weekend.
>
> Mogens
> --
> Mogens Kjaer, Carlsberg A/S, Computer Department
> Gamle Carlsberg Vej 10, DK-2500 Valby, Denmark
> Phone: +45 33 27 53 25, Mobile: +45 22 12 53 25
> Email: mk at crc.dk Homepage: http://www.crc.dk
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