Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I got disk failure on my Centos Linux soft raid 5 array (mdadm). I replaced one of the disk and started to rebuild the array. Next time I checked the status, the rebuild was failed.

This is the status right now:

[root@localhost ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : inactive sdc1[3](S) sdd1[2] sdb1[0]
      4883277760 blocks

unused devices: <none>


[root@localhost ~]# mdadm --detail /dev/md0
        Version : 0.90
  Creation Time : Mon Aug 23 22:37:36 2010
     Raid Level : raid5
  Used Dev Size : 1465135936 (1397.26 GiB 1500.30 GB)
   Raid Devices : 3
  Total Devices : 3
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Tue Jan  1 23:30:32 2002
          State : active, degraded, Not Started
 Active Devices : 2
Working Devices : 3
 Failed Devices : 0
  Spare Devices : 1

         Layout : left-symmetric
     Chunk Size : 64K

           UUID : 6af06755:6fc93cba:c083764e:1e719c94
         Events : 0.27470

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

       3       8       33        -      spare   /dev/sdc1

/dev/sdc is the brand new drive. If I try to remove it and add again, it still stays in spare. How should I try to start rebuild this?

share|improve this question
Could you try to remove failed/detached devices with 'mdadm /dev/md0 --remove failed' and 'mdadm /dev/md0 --remove detached' and to dump details again? – dsmsk80 Feb 24 '14 at 19:33
Tried to remove failed and detached disks but no change to md0 details. Btw. im in read only filesystem, this should not affect? – devha Feb 24 '14 at 20:01
So the line with "removed" device is still there? – dsmsk80 Feb 24 '14 at 20:06
Yes, no change to mdadm --detail /dev/md0 output. – devha Feb 24 '14 at 20:10

How should I try to start rebuild this?

Depends on if you care about the data. Assuming you do, there is a guide over here. Note that RAID-5 has some issues, which were enough for me to convert most of our environment to RAID-10 or just plain mirrors.

I'm not sure what /dev/md0 is, but if your root (/) filesystem is on there (or any filesystem you're distribution would need, like /usr for the utilities), then I would suggest you get a Live-Boot CD for your Linux Distribution and boot-off of that before attempting a repair.

Once you've rebooted off of a Boot-CD, run the following to find your array;

mdadm --assemble --scan

From there, you can either follow the guide above in an attempt to safely recover the RAID-5 array. Or you can nuke and rebuild the entire thing.

Note that you might want to consider a more redundant configuration, such as RAID-1 & a spare. (Unless you can get a 4th drive, then RAID-10)

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.