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I am running a home server with three RAID1 arrays, each with two drives: md0, md1 and md127. After an accidental reboot, md0 and md1 are running on one device only, and I cannot add back the respective second device.

These are the arrays:

  • md0: /dev/sdg1, /dev/sdi1
  • md1: /dev/sdf1, /dev/sdd1
  • md127: /dev/sdh, /dev/sdb1

Here is the output of lsblk:

NAME      MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda         8:0    0   3.7T  0 disk  
sdb         8:16   0   1.8T  0 disk  
└─sdb1      8:17   0   1.8T  0 part  
  └─md127   9:127  0   1.8T  0 raid1 
sdc         8:32   0 465.8G  0 disk  
└─sdc1      8:33   0 465.8G  0 part  
sdd         8:48   0 931.5G  0 disk  
└─sdd1      8:49   0 931.5G  0 part  
sde         8:64   0   2.7T  0 disk  
└─sde1      8:65   0   2.7T  0 part  
sdf         8:80   0 931.5G  0 disk  
└─sdf1      8:81   0 931.5G  0 part  
  └─md1     9:1    0 931.4G  0 raid1 
sdg         8:96   0 465.8G  0 disk  
└─sdg1      8:97   0 465.8G  0 part  
  └─md0     9:0    0 465.6G  0 raid1 /
sdh         8:112  0   1.8T  0 disk  
└─sdh1      8:113  0   1.8T  0 part  
  └─md127   9:127  0   1.8T  0 raid1 
sdi         8:128  1 465.8G  0 disk  
└─sdi1      8:129  1 465.8G  0 part  
sdj         8:144  1  29.8G  0 disk  
└─sdj1      8:145  1  29.8G  0 part  [SWAP]

This is the status of the two arrays with problems:

/dev/md0:
        Version : 1.2
  Creation Time : Sat Apr 13 18:47:42 2019
     Raid Level : raid1
     Array Size : 488244864 (465.63 GiB 499.96 GB)
  Used Dev Size : 488244864 (465.63 GiB 499.96 GB)
   Raid Devices : 2
  Total Devices : 1
    Persistence : Superblock is persistent

  Intent Bitmap : Internal

    Update Time : Sun Sep  1 20:12:17 2019
          State : clean, degraded 
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

           Name : GC01SRVR:0  (local to host GC01SRVR)
           UUID : 21f37e07:aea8dfec:e78b69d7:46f70c4d
         Events : 399869

    Number   Major   Minor   RaidDevice State
       -       0        0        0      removed
       1       8       97        1      active sync   /dev/sdg1


/dev/md1:
        Version : 1.2
  Creation Time : Sat Apr 13 18:50:33 2019
     Raid Level : raid1
     Array Size : 976628736 (931.39 GiB 1000.07 GB)
  Used Dev Size : 976628736 (931.39 GiB 1000.07 GB)
   Raid Devices : 2
  Total Devices : 1
    Persistence : Superblock is persistent

  Intent Bitmap : Internal

    Update Time : Sun Sep  1 20:02:33 2019
          State : clean, degraded 
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

           Name : GC01SRVR:1  (local to host GC01SRVR)
           UUID : e0e49af7:7a791be6:168f01ab:6e84ba17
         Events : 899185

    Number   Major   Minor   RaidDevice State
       -       0        0        0      removed
       1       8       81        1      active sync   /dev/sdf1

This is the output of mdadm.conf: it makes me suspicious as there are only two arrays listed.

# definitions of existing MD arrays
ARRAY /dev/md/1  metadata=1.2 UUID=e0e49af7:7a791be6:168f01ab:6e84ba17 name=GC01SRVR:1
ARRAY /dev/md/0  metadata=1.2 UUID=21f37e07:aea8dfec:e78b69d7:46f70c4d name=GC01SRVR:0

How can I add back the missing drives to their respective arrays, considering that md0 is where the operating system lives?

  • Which devices should belong to which arrays? Have you tried anything at all? ("no" is an acceptable answer; but if "yes" please explain exactly what). – roaima Sep 1 '19 at 18:23
  • I have added the arrays with their drives in the question. I have tried the --assemble option. – giovi321 Sep 1 '19 at 18:26
  • What does mdadm --examine show for /dev/sdd1, /dev/sdf1, /dev/sdg1, and /dev/sdi1? – Mark Sep 10 '19 at 2:52

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