Bug#495580: mdadm: 4 disk raid10 with 1 active and 3 spare possible

Mon Aug 18 18:42:16 UTC 2008

Package: mdadm
Version: 2.6.7-3
Severity: important

Hello,

I played recently around with the Linux software RAID for grub2, I had never
before that much to do with it so maybe I did something wrong.
But in any case it shouldn't be that easy to get a broken RAID 10 :)

It's more from my memory and .bash_history now, I didn't do it now exactly that way again.

I made a 4 disk RAID 10 with:
# mdadm -C -l10 -n4 /dev/md0 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1

Then I just set one after one faulty and removed them and then added it back
again.

# mdadm -f /dev/sdc1
# mdadm -r /dev/sdc1
# mdadm -a /dev/sdc1

Before I stopped it I luckly did a -Q --detail see below
I can't reassemble it now:

mdadm: /dev/md0 assembled from 1 drive and 3 spares - not enough to start the
array.

I even tried before stopping the RAID, a --update=resync but that didn't change
anything.

mdadm --grow -n4 didn't work either, unfortunately I don't have the output
anymore.

# mdadm -Q --detail /dev/md0

/dev/md0:
        Version : 00.90
  Creation Time : Mon Aug 18 18:17:19 2008
     Raid Level : raid10
     Array Size : 16771584 (15.99 GiB 17.17 GB)
  Used Dev Size : 8385792 (8.00 GiB 8.59 GB)
   Raid Devices : 4
  Total Devices : 4
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Mon Aug 18 20:13:58 2008
          State : clean, degraded
 Active Devices : 1
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 3

         Layout : near=2, far=1
     Chunk Size : 64K

           UUID : 2b2e94e0:ec27865c:89ccbef7:ff5abfb0 (local to host fz-vm)
         Events : 0.448

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

       4       8       81        -      spare   /dev/sdf1
       5       8       65        -      spare   /dev/sde1
       6       8       33        -      spare   /dev/sdc1

-- Package-specific info:
--- mount output
/dev/sda1 on / type ext4dev (rw,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
/proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
fusectl on /sys/fs/fuse/connections type fusectl (rw)
root at fz:/home/fz on /home/fz type fuse.sshfs (rw,nosuid,nodev,max_read=65536,allow_other)

--- mdadm.conf
# mdadm.conf
#
# Please refer to mdadm.conf(5) for information about this file.
#

# by default, scan all partitions (/proc/partitions) for MD superblocks.
# alternatively, specify devices to scan, using wildcards if desired.
DEVICE partitions

# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes

# automatically tag new arrays as belonging to the local system
HOMEHOST <system>

# instruct the monitoring daemon where to send mail alerts
MAILADDR root

# This file was auto-generated on Mon, 28 Jul 2008 21:44:39 +0200
# by mkconf $Id$

--- /proc/mdstat:
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] 
md0 : inactive sdd1[1](S) sdc1[6](S) sde1[5](S) sdf1[4](S)
      33543168 blocks

unused devices: <none>

--- /proc/partitions:
major minor  #blocks  name

   8     0    8388608 sda
   8     1    8385898 sda1
   8    16    8388608 sdb
   8    17    8385898 sdb1
   8    32    8388608 sdc
   8    33    8385898 sdc1
   8    48    8388608 sdd
   8    49    8385898 sdd1
   8    64    8388608 sde
   8    65    8385898 sde1
   8    80    8388608 sdf
   8    81    8385898 sdf1

--- initrd.img-2.6.27-rc3:

--- /proc/modules:

--- volume detail:

--- /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-2.6.27-rc3 root=/dev/sda1 ro vga=0x317

-- System Information:
Debian Release: lenny/sid
  APT prefers experimental
  APT policy: (500, 'experimental'), (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.27-rc3 (SMP w/2 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages mdadm depends on:
ii  debconf                   1.5.23         Debian configuration management sy
ii  libc6                     2.8+20080809-1 GNU C Library: Shared libraries
ii  lsb-base                  3.2-19         Linux Standard Base 3.2 init scrip
ii  makedev                   2.3.1-88       creates device files in /dev
ii  udev                      0.125-5        /dev/ and hotplug management daemo

Versions of packages mdadm recommends:
pn  mail-transport-agent          <none>     (no description available)
ii  module-init-tools             3.4-1      tools for managing Linux kernel mo

mdadm suggests no packages.

-- debconf information:
  mdadm/initrdstart_msg_errexist:
  mdadm/initrdstart_msg_intro:
* mdadm/autostart: false
* mdadm/autocheck: false
  mdadm/initrdstart_msg_errblock:
  mdadm/mail_to: root
  mdadm/initrdstart_msg_errmd:
* mdadm/initrdstart: all
  mdadm/initrdstart_msg_errconf:
  mdadm/initrdstart_notinconf: false
* mdadm/start_daemon: false