tracking parity mismatches to a failing disk

I'm trying to identify the source of a non-zero mismatch_cnt on a
six-disk RAID6 md array.  I think I've identified it as /dev/sdf since
that is the only device with a non-zero value in
/sys/block/md0/md/dev-sd*/errors.  Is that the right way to track parity
mismatches back to a disk?

OS is CentOS 5.8 -> mdadm 2.6.9

Thanks,
Michael