WARNING: mismatch_cnt is not 0 on /dev/md1


Since a couple of days I have seen the following message on (CentOS) servers:

WARNING: mismatch_cnt is not 0 on /dev/md1

I have Googled some around, posted on forums, but couldn’t find the cause of this.
Anyways, I managed to fix it with a workaround:

# echo repair >/sys/block/md1/md/sync_action
# wait a bit ….
# echo check >/sys/block/md1/md/sync_action 

Should be fixed now!

If you know what it exactly means and what the reason is, let me know please!