Trouble Re-Building RAID 5 with mdadm

machejc · 04-05-2015, 09:50 PM

I am running Fedora 15 and lost a disk drive (dev/sde1) on my 4 device RAID 5.

I replaced the failed drive with a new one and re-added that drive in.

Code:

# # mdadm --manage /dev/md127 -a /dev/sde1
mdadm: added /dev/sde1

Now the current status is:

Code:

# mdadm --detail /dev/md127
/dev/md127:
        Version : 0.90
  Creation Time : Tue Sep 30 13:58:53 2008
     Raid Level : raid5
  Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
   Raid Devices : 4
  Total Devices : 4
Preferred Minor : 127
    Persistence : Superblock is persistent

    Update Time : Sun Apr  5 19:10:48 2015
          State : active, degraded, Not Started
 Active Devices : 3
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 1

         Layout : left-symmetric
     Chunk Size : 64K

           UUID : 653d0b4b:86db92d1:2be201d9:114acb0f
         Events : 0.4860502

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

       4       8       65        -      spare   /dev/sde1

How do I remove the Number 2 removed and get /dev/sde1 to be re-added into the /dev/md127 RAID 5 and have it start rebuilding?

Keruskerfuerst · 04-06-2015, 05:23 AM

You should use the option --re-add.

machejc · 04-06-2015, 01:35 PM

It did not work. Now what?

How do I get rid of the Number 2 removed device?

Code:

# mdadm --manage /dev/md127 --remove /dev/sde1
mdadm: hot removed /dev/sde1 from /dev/md127
#
# mdadm --detail /dev/md127
/dev/md127:
        Version : 0.90
  Creation Time : Tue Sep 30 13:58:53 2008
     Raid Level : raid5
  Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
   Raid Devices : 4
  Total Devices : 3
Preferred Minor : 127
    Persistence : Superblock is persistent

    Update Time : Mon Apr  6 11:28:44 2015
          State : active, degraded, Not Started
 Active Devices : 3
Working Devices : 3
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

           UUID : 653d0b4b:86db92d1:2be201d9:114acb0f
         Events : 0.4860504

    Number   Major   Minor   RaidDevice State
       0       8       33        0      active sync   /dev/sdc1
       1       8       17        1      active sync   /dev/sdb1
       2       0        0        2      removed
       3       8       49        3      active sync   /dev/sdd1
#
# mdadm --manage /dev/md127 --re-add /dev/sde1
mdadm: --re-add for /dev/sde1 to /dev/md127 is not possible
#
# mdadm --manage /dev/md127 --re-add /dev/sde1
mdadm: --re-add for /dev/sde1 to /dev/md127 is not possible
# mdadm --detail /dev/md127
/dev/md127:
        Version : 0.90
  Creation Time : Tue Sep 30 13:58:53 2008
     Raid Level : raid5
  Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
   Raid Devices : 4
  Total Devices : 3
Preferred Minor : 127
    Persistence : Superblock is persistent

    Update Time : Mon Apr  6 11:28:44 2015
          State : active, degraded, Not Started
 Active Devices : 3
Working Devices : 3
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

           UUID : 653d0b4b:86db92d1:2be201d9:114acb0f
         Events : 0.4860504

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

machejc · 04-06-2015, 09:18 PM

Fixed!!

Code:

# mdadm --stop /dev/md127
# mdadm --assemble  -f -R /dev/md127

The new drive was accepted by the RAID and is rebuilding.