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Hoping someone can help! Never used software raid before and I've noticed the 2 disk RAID 1 is showing as degraded [U_] :

# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sda3[0]
      3905836032 blocks super 1.2 [2/1] [U_]
      bitmap: 29/30 pages [116KB], 65536KB chunk

md0 : active raid1 sda2[0]
      1046528 blocks super 1.2 [2/1] [U_]
      bitmap: 1/1 pages [4KB], 65536KB chunk

unused devices: <none>

I'm having trouble finding if a disk has failed or what has happened. Both disks are visible and testing fine with smartctl.

Here is the mdadm --detail output: 

# mdadm --detail /dev/md0
/dev/md0:
           Version : 1.2
     Creation Time : Mon Sep  9 17:04:24 2019
        Raid Level : raid1
        Array Size : 1046528 (1022.00 MiB 1071.64 MB)
     Used Dev Size : 1046528 (1022.00 MiB 1071.64 MB)
      Raid Devices : 2
     Total Devices : 1
       Persistence : Superblock is persistent

     Intent Bitmap : Internal

       Update Time : Tue Sep 10 16:01:36 2019
             State : clean, degraded
    Active Devices : 1
   Working Devices : 1
    Failed Devices : 0
     Spare Devices : 0

Consistency Policy : bitmap

              Name : xxx:0  (local to host xxx)
              UUID : 40713c03:b0a45738:aae59e3a:541556fe
            Events : 117

    Number   Major   Minor   RaidDevice State
       0       8        2        0      active sync   /dev/sda2
       -       0        0        1      removed


# mdadm --detail /dev/md1
    /dev/md1:
               Version : 1.2
         Creation Time : Mon Sep  9 17:03:48 2019
            Raid Level : raid1
            Array Size : 3905836032 (3724.90 GiB 3999.58 GB)
         Used Dev Size : 3905836032 (3724.90 GiB 3999.58 GB)
          Raid Devices : 2
         Total Devices : 1
           Persistence : Superblock is persistent

         Intent Bitmap : Internal

           Update Time : Tue Sep 10 16:51:52 2019
                 State : active, degraded
        Active Devices : 1
       Working Devices : 1
        Failed Devices : 0
         Spare Devices : 0

    Consistency Policy : bitmap

                  Name : xxx:1  (local to host xxx)
                  UUID : c76c221f:33fff959:e95e90d6:f350c30b
                Events : 71886

        Number   Major   Minor   RaidDevice State
           0       8        3        0      active sync   /dev/sda3
           -       0        0        1      removed

I understand I can resync the array, but I'm unclear even as to what is missing.

Thanks for any advice!

--

Edit - After taking Stephens advice, it now looks like this:

I guess it would have helped if I could see what it used to look like..

It looks like this after running those commands:

# mdadm --detail /dev/md0

    Number   Major   Minor   RaidDevice State
       0       8        2        0      active sync   /dev/sda2
       1       8       18        1      active sync   /dev/sdb2
# mdadm --detail /dev/md1

    Number   Major   Minor   RaidDevice State
       0       8        3        0      active sync   /dev/sda3
       1       8       19        1      spare rebuilding   /dev/sdb3

Looks to have sorted the issue :)

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1 Answer 1

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What’s missing is the second disk. Both MD devices are using partitions on /dev/sda, and presumably they used to have mirrors on another device...

Do you have another disk? Is it still working?

Once you’ve figured out what the situation is, and either confirmed that the existing disk is working, or replaced it (and created the partitions again), you should use

sudo mdadm --add /dev/md0 /dev/sdb2

and

sudo mdadm --add /dev/md1 /dev/sdb3

to restore the arrays to their nominal state.

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  • 1
    Don't Forget to check if the second disk has Errors: "smartctl -a /dev/sdb" Commented Sep 10, 2019 at 17:56

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