[Bug 285156] Re: mdadm RAID10 arrays cannot be rebuilt, will not use available spare drives

Thu Aug 11 07:43:26 UTC 2011

** Changed in: debian
       Status: Unknown => Fix Released

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Title:
  mdadm RAID10 arrays cannot be rebuilt, will not use available spare
  drives

Status in The Linux Kernel:
  Fix Released
Status in “linux” package in Ubuntu:
  Fix Released
Status in “mdadm” package in Ubuntu:
  Invalid
Status in “linux” source package in Intrepid:
  Fix Released
Status in “mdadm” source package in Intrepid:
  Invalid
Status in “linux” source package in Jaunty:
  Fix Released
Status in “mdadm” source package in Jaunty:
  Invalid
Status in Debian GNU/Linux:
  Fix Released

Bug description:
  Binary package hint: mdadm

  Rebuild degraded RAID1 or RAID5 no problem, rebuild degraded RAID10
  fails.

  Here is basic problem, one drive fails leaving RAID10 array and
  clean/degraded. Add hot spare. Drive shows up as hot spare yet auto-
  rebuild does not start. Only occurs with RAID10 array. I try removing
  the spare drive, delete its super block, and then re-add it, stll
  fails. Do the same thing with RAID1/RAID5 and auto-rebuild starts on
  its own.

  This is using Ubuntu 8.10 and mdadm 2.6.7-3ubuntu7.

  Here is example:
  bexamous at nine:~/bin$ sudo mdadm /dev/md4 --remove /dev/sdb4
  mdadm: hot removed /dev/sdb4
  bexamous at nine:~/bin$ sudo mdadm --zero-superblock /dev/sdb4
  bexamous at nine:~/bin$ sudo mdadm /dev/md4 --add /dev/sdb4
  mdadm: added /dev/sdb4
  bexamous at nine:~/bin$ cat /proc/mdstat 
  Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
  md2 : active raid0 sdb2[0] sdd2[2] sdc2[1]
        733767168 blocks 512k chunks

  md3 : active raid5 sdb3[0] sdc3[1] sdd3[6] sdh3[5] sdg3[4] sdf3[3] sde3[2]
        4300824576 blocks level 5, 512k chunk, algorithm 2 [7/7] [UUUUUUU]

  md4 : active raid10 sdb4[7](S) sdc4[1] sdh4[6] sdg4[5] sdf4[4] sde4[3] sdd4[2]
        53781280 blocks 32K chunks 2 near-copies [7/6] [_UUUUUU]

  unused devices: <none>
  bexamous at nine:~/bin$

  Here is array --detail
  /dev/md4:
          Version : 00.90
    Creation Time : Mon Oct 13 02:01:54 2008
       Raid Level : raid10
       Array Size : 53781280 (51.29 GiB 55.07 GB)
    Used Dev Size : 15366080 (14.65 GiB 15.73 GB)
     Raid Devices : 7
    Total Devices : 7
  Preferred Minor : 4
      Persistence : Superblock is persistent

      Update Time : Thu Oct 16 11:52:39 2008
            State : clean, degraded
   Active Devices : 6
  Working Devices : 7
   Failed Devices : 0
    Spare Devices : 1

           Layout : near=2, far=1
       Chunk Size : 32K

             UUID : c16f9559:800b499b:18ceddb4:39b7cf2e (local to host nine)
           Events : 0.32

      Number   Major   Minor   RaidDevice State
         0       0        0        0      removed
         1       8       36        1      active sync   /dev/sdc4
         2       8       52        2      active sync   /dev/sdd4
         3       8       68        3      active sync   /dev/sde4
         4       8       84        4      active sync   /dev/sdf4
         5       8      100        5      active sync   /dev/sdg4
         6       8      116        6      active sync   /dev/sdh4

         7       8       20        -      spare   /dev/sdb4

  Here is another example of fail to rebuild RAID10 and then success in rebuilting as RAID1:
  root at nine:~# cat /proc/mdstat 
  Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
  md9 : active raid10 loop4[3] loop3[2] loop2[1] loop1[0]
        40832 blocks 64K chunks 2 near-copies [4/4] [UUUU]

  unused devices: <none>
  root at nine:~# mdadm /dev/md9 -f /dev/loop3
  mdadm: set /dev/loop3 faulty in /dev/md9
  root at nine:~# cat /proc/mdstat 
  Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
  md9 : active raid10 loop4[3] loop3[4](F) loop2[1] loop1[0]
        40832 blocks 64K chunks 2 near-copies [4/3] [UU_U]
  root at nine:~# mdadm /dev/md9 --remove /dev/loop3
  mdadm: hot removed /dev/loop3
  root at nine:~# cat /proc/mdstat 
  Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
  md9 : active raid10 loop4[3] loop2[1] loop1[0]
        40832 blocks 64K chunks 2 near-copies [4/3] [UU_U]
  root at nine:~# mdadm --zero-superblock /dev/loop3
  root at nine:~# mdadm /dev/md9 --add /dev/loop3
  mdadm: added /dev/loop3
  root at nine:~# cat /proc/mdstat 
  Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
  md9 : active raid10 loop3[4](S) loop4[3] loop2[1] loop1[0]
        40832 blocks 64K chunks 2 near-copies [4/3] [UU_U]
  root at nine:~#

  root at nine:~# mdadm -S /dev/md9
  mdadm: stopped /dev/md9
  root at nine:~# mdadm --zero-superblock /dev/loop1
  root at nine:~# mdadm --zero-superblock /dev/loop2
  root at nine:~# mdadm --zero-superblock /dev/loop3
  root at nine:~# mdadm --zero-superblock /dev/loop4
  root at nine:~# mdadm -C --level=raid1 -n 4 /dev/md9 /dev/loop1 /dev/loop2 /dev/loop3 /dev/loop4
  mdadm: array /dev/md9 started.
  root at nine:~# cat /proc/mdstat 
  md9 : active raid1 loop4[3] loop3[2] loop2[1] loop1[0]
        20416 blocks [4/4] [UUUU]
  root at nine:~# mdadm /dev/md9 -f /dev/loop3
  mdadm: set /dev/loop3 faulty in /dev/md9
  root at nine:~# mdadm /dev/md9 --remove /dev/loop3
  mdadm: hot removed /dev/loop3
  root at nine:~# mdadm /dev/md9 --zero-superblock /dev/loop3
  root at nine:~# mdadm /dev/md9 --add /dev/loop3
  mdadm: added /dev/loop3
  root at nine:~# cat /proc/mdstat 
  md9 : active raid1 loop3[2] loop4[3] loop2[1] loop1[0]
        20416 blocks [4/4] [UUUU]

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