On Thu, 21 Apr 2011 08:00:39 -0500 Andrew Falgout <andrew.falgout@xxxxxxxxx> wrote: > I got an error last week from a new raid6 array about a mismatch_cnt. I > did some reading online, performed a repair action on the array, > performed a check action, and checked for the mismatch_cnt again. The > number was greatly reduced, but it was still there. According to mdadm, > everything appears to be working fine. All the drives are passing short > tests on smartctl. > > What is mismatch_cnt really? Should I even be concerned about this? Yes, you should be concerned. mismatch_cnt is a count of sectors where the parity blocks don't match the data blocks. The code doesn't check every sector individually. For raid5/6 it checks 4K at a time, so divide by 8, and that many 4K blocks are in doubt. So something if going wrong somewhere. I would run 'check' a few time and see if the number changes. If it goes down at all, then it looks like you occasionally get bad reads from a device. If it only ever increases, then you are presumably getting bad writes sometimes. You could: - stop the array - run sha1sum on each member disk, several times. - if any one disk has an unstable result - check cabling, or replace the disk - if more than one disk has an unstable result, replace the controller maybe. - if all results are stable it must be a write-only problem - much harder to work with. NeilBrown > The array is giving me 25-30MB/sec performance on an sshfs mount over > the network. With a local copy I can see speeds of 50 to 60MB/sec. > > Thanks, > Andrew Falgout -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
