16.21. Repairing RAID disks

Procedure

1. Check the array for the failed disks behavior:

   # echo check > /sys/block/md0/md/sync_action

   This checks the array and the /sys/block/md0/md/sync_action file shows the sync action.

2. Open the /sys/block/md0/md/sync_action file with the text editor of your choice and see if there is any message about disk synchronization failures.
3. View the /sys/block/md0/md/mismatch_cnt file. If the mismatch_cnt parameter is not 0, it means that the RAID disks need repair.

4. Repair the disks in the array:

   # echo repair > /sys/block/md0/md/sync_action

   This repairs the disks in the array and writes the result into the /sys/block/md0/md/sync_action file.

5. View the synchronization progress:

   # cat /sys/block/md0/md/sync_action
   repair
   
   # cat /proc/mdstat
   Personalities : [raid0] [raid6] [raid5] [raid4] [raid1]
   md0 : active raid1 sdg[1] dm-3[0]
         511040 blocks super 1.2 [2/2] [UU]
   unused devices: <none>