mdadm removed and spare disk

Uruz42 · 08-13-2015, 01:05 PM

Hey folks,

I have a mdadm raid 6 array, and it seems that it is somehow degraded or has issues of some other kind.
It used to be a raid 6 array of 5 disks. However it seems that somehow (probaly becouse I screwed something up) one of the drives is removed and added as a spare. I have tried fixing it by using --re-add or --add but all seems to not really work.
Below the --detail and /proc/mdstat

Code:

# mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Tue Oct  7 22:08:51 2014
     Raid Level : raid6
  Used Dev Size : -1
   Raid Devices : 5
  Total Devices : 5
    Persistence : Superblock is persistent

    Update Time : Thu Aug 13 14:34:06 2015
          State : active, degraded, Not Started
 Active Devices : 4
Working Devices : 5
 Failed Devices : 0
  Spare Devices : 1

         Layout : left-symmetric
     Chunk Size : 512K

           Name : debian-name:0  (local to host debian-name)
           UUID : cb730507:61aed11d:c7804066:8a28886b
         Events : 155

    Number   Major   Minor   RaidDevice State
       0       8       65        0      active sync   /dev/sde1
       1       0        0        1      removed
       2       8       17        2      active sync   /dev/sdb1
       3       8       33        3      active sync   /dev/sdc1
       4       8       49        4      active sync   /dev/sdd1

       5       8        1        -      spare   /dev/sda1

Code:

~# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : inactive sde1[0] sda1[5](S) sdd1[4] sdc1[3] sdb1[2]
      14650670080 blocks super 1.2

My guiss is that it will not be that hard but as all my data is on it I prefere to not use trial and error too much.
Thanks in advance for the help.

lazydog · 08-13-2015, 01:13 PM

Try the following (assuming that the disk removed if f):

Code:

mdadm --zero-superblock /dev/sdf1
mdadm /dev/md0 --add /dev/sdf1

Uruz42 · 08-13-2015, 01:26 PM

First of all thanks for the reply. I tried doing so however it seems that it is unavailable for opening. So to be shure I did a reboot.

Code:

~# mdadm --zero-superblock /dev/sda1
mdadm: Couldn't open /dev/sda1 for write - not zeroing

Just to make shure after rebooting I did detail again and it seems the disks are somehow renamed for now sdb1 is the dead link instead of sda1

Code:

# mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Tue Oct  7 22:08:51 2014
     Raid Level : raid6
  Used Dev Size : -1
   Raid Devices : 5
  Total Devices : 5
    Persistence : Superblock is persistent

    Update Time : Thu Aug 13 14:34:06 2015
          State : active, degraded, Not Started
 Active Devices : 4
Working Devices : 5
 Failed Devices : 0
  Spare Devices : 1

         Layout : left-symmetric
     Chunk Size : 512K

           Name : debian-hidde:0  (local to host debian-hidde)
           UUID : cb730507:61aed11d:c7804066:8a28886b
         Events : 155

    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   /dev/sda1
       1       0        0        1      removed
       2       8       33        2      active sync   /dev/sdc1
       3       8       49        3      active sync   /dev/sdd1
       4       8       65        4      active sync   /dev/sde1

       5       8       17        -      spare   /dev/sdb1

Once again I tried --zero-superblock but still doesnt work.

Code:

# mdadm --zero-superblock /dev/sdb1
mdadm: Couldn't open /dev/sdb1 for write - not zeroing

I'm wondering if it's rebuilding or something so all the disks cannot be accesed?
Also for my learning purpouses, am I correct if I say that what you intended was deleting the removed disk and deleting all data from it so that it can be added?

lazydog · 08-14-2015, 12:34 PM

What does the following spit out;

Code:

cat /proc/mdstat

Also check the disk to ensure it is set to Linux Raid