I recently got an automated email saying "WARNING: mismatch_cnt is not 0 on /dev/md3".
I'm running a software RAID5 array using mdadm on CentOS 6.6
When Googling the message I found this:-
The check operation scans the drives for bad sectors and automatically repairs them. If it finds good sectors that contain bad data (the data in a sector does not agree with what the data from another disk indicates that it should be, for example the parity block + the other data blocks would cause us to think that this data block is incorrect), then no action is taken, but the event is logged. This "do nothing" allows admins to inspect the data in the sector and the data that would be produced by rebuilding the sectors from redundant information and pick the correct data to keep.
My question is, how do I inspect the data and pick the correct data to keep? There doesn't seem to be any mention of how to do this anywhere and I have no idea what files these sectors are affecting