One of the advantages of running a Linux RAID configuration is that it simplifies clearing of UNC errors on your hard disks. If you have such a setup, you may follow the process below to clear the UNC errors from your disk and extends it's life a bit longer. The example here is for a RAID 1 configuration, but any RAID level will do (besides RAID 0).
Determine the disk (X) with the errors using smartctl
smartctl -A /dev/sda smartctl -A /dev/sdb
Determine the LBA where the first error was found
smartctl -a /dev/sdX
Determine the partition (Y) that contains the LBA
sfdisk -l -uS /dev/sdX
Do not continue this process if there are excessive errors (80 or more). Replace the disk immediately.
Determine the RAID array (Z) that the partition belongs to
Fail and remove the partition from the RAID
mdadm /dev/mdZ --fail /dev/sdXY mdadm /dev/mdZ --remove /dev/sdXY
You must zero the superblocks on the partition to allow a proper remirror
mdadm --zero-superblock /dev/sdXY
Re-add the partition to the RAID to initiate the remirror
mdadm /dev/mdZ --add /dev/sdXY
Monitor the remirror progress. When complete, review smartctl to see if the errors are gone.
- If errors are still there, confirm you have been working with the correct partition
- If all errors cannot be cleared, replace the disk.
When all errors are cleared, run a long SMART test to confirm disk is healthy.
smartctl -t long /dev/sdX
It should complete without any read errors.
- If more errors are found. Repeat the process above.
- Do not repeat the process any more than 2 times. The drive is unhealthy at this point and should be replaced.
- Do not repeat the process if there are excessive errors (80 or more).