RAID5 degraded, but SMART shows all drives 'passed' test

  • Had a bad thunderstorm in my area last night that resulted in a power outage. After OMV restart, once the power was restored, I noticed one of my two RAID 5 arrays was offline. After some fiddling, I got it back online but with 2 out of 3 drives. SMART shows all 3 of the drives 'passed'. I'm running OMV 3.0.99 with kernel 4.9.0.


    Here is the mdadm --misc --query --examine for each drive in the array. /sde is the drive excluded from the array


    Here's the cat /proc/mdstat

    Code
    md126 : active raid5 sdd[0] sdg[2] sdf[1]
          5860270080 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
          [============>........]  resync = 63.9% (1875104952/2930135040) finish=167.8min speed=104764K/sec
    
    
    md127 : active raid5 sdb[0] sda[3]
          3906765824 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/2] [U_U]
    
    
    unused devices: <none>


    blkid


    Finally here is the mdadm --detail --scan --verbose

    Code
    root@openmediavault:~# mdadm --detail --scan --verbose
    ARRAY /dev/md127 level=raid5 num-devices=3 metadata=1.2 name=omvnas:Server UUID=be9d6a6e:3d6f3e23:fee9a740:47a5fefb
       devices=/dev/sda,/dev/sdb
    ARRAY /dev/md126 level=raid5 num-devices=3 metadata=1.2 name=omvnas:Media UUID=bbd69834:ff0ce5ad:7ae15eba:53319b53
       devices=/dev/sdd,/dev/sdf,/dev/sdg


    I have no idea if the drive is actually good or bad, or how to fix this issue.

  • If you believe the drive is still good, you can overwrite the first blocks of that drive and readd to the raid.


    It is currently in failed mode and still has the raid header on it.


    So you can run dd if=/dev/zero of=/dev/sde count=10 bs=1M


    That will overwrite the first 10M of your drive with zeros.


    After that you can rejoin the disk to your array md127 and the resync will start.


    Hope that helps.

    Everything is possible, sometimes it requires Google to find out how.

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