new raid /dev/md0 disappears after reboot!

**Drunken** · July 26th, 2009

Hi, whenever I set up a new raid0, it works fine, until I reboot and try to mount it again. Here's what I did to set it up:

(note /dev/sdc is my main drive, sda and sdb are new SATA harddrives)

Code:

#fdisk /dev/sda
Command (m for help): n (create a new primary partition)
Command (m for help): t (then select da for "non-fs data")
Command (m for help): w (write changes to disk and quit)

#fdisk /dev/sdb
Command (m for help): n (create a new primary partition)
Command (m for help): t (then select da for "non-fs data")
Command (m for help): w (write changes to disk and quit)

Code:

#mdadm --create --verbose /dev/md0 --level=stripe --raid-devices=2 /dev/sda1 /dev/sdb1
#mkfs.ext3 /dev/md0
#mkdir /raid1
#mount /dev/md0 /raid1

And here all works successfully.
But when I restart, /dev/md0 is gone.
This is on a clean Ubuntu 9 x86 installation.

Also here is some information about the system before I do the restart:

Code:

root@ubuntu-raid:~# cat /proc/mdstat
Personalities : [raid0]
md0 : active raid0 sdb1[1] sda1[0]
      8385664 blocks 64k chunks

unused devices: <none>

Code:

root@ubuntu-raid:~# cat /etc/mdadm/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

# definitions of existing MD arrays

# This file was auto-generated on Sun, 26 Jul 2009 16:16:31 -0400
# by mkconf $Id$

Code:

root@ubuntu-raid:~# mdadm --query --detail /dev/md0
/dev/md0:
        Version : 00.90
  Creation Time : Sun Jul 26 16:18:35 2009
     Raid Level : raid0
     Array Size : 8385664 (8.00 GiB 8.59 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Sun Jul 26 16:18:35 2009
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

     Chunk Size : 64K

           UUID : 6b402e82:fec208ab:c4e69391:c984b73c (local to host ubuntu-raid)
         Events : 0.1

    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   /dev/sda1
       1       8       17        1      active sync   /dev/sdb1

...now I reboot the machine (#shutdown -r now).

During reboot, I see a message saying

Code:

Starting MD monitoring service mdadm --monitor               [ OK ]

which I believe is a good thing.
Now back at the shell I type:

Code:

root@ubuntu-raid:~# ls /dev/md* -l
brw-rw---- 1 root disk 254, 0 2009-07-26 16:26 /dev/md_d0
lrwxrwxrwx 1 root root      7 2009-07-26 16:26 /dev/md_d0p1 -> md/d0p1
lrwxrwxrwx 1 root root      7 2009-07-26 16:26 /dev/md_d0p2 -> md/d0p2
lrwxrwxrwx 1 root root      7 2009-07-26 16:26 /dev/md_d0p3 -> md/d0p3
lrwxrwxrwx 1 root root      7 2009-07-26 16:26 /dev/md_d0p4 -> md/d0p4

/dev/md:
total 0
brw------- 1 root root 254, 0 2009-07-26 16:26 d0
brw------- 1 root root 254, 1 2009-07-26 16:26 d0p1
brw------- 1 root root 254, 2 2009-07-26 16:26 d0p2
brw------- 1 root root 254, 3 2009-07-26 16:26 d0p3
brw------- 1 root root 254, 4 2009-07-26 16:26 d0p4

And no /dev/md0 exists anymore!

Also mdstat shows this

Code:

root@ubuntu-raid:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md_d0 : inactive sda1[0](S)
      4192832 blocks

unused devices: <none>

Any suggestions on what I am doing wrong would be greatly appreciated.
Thanks.

**miegiel** · July 26th, 2009

Are you sure mdadm loads during boot up? If you delete the splash parameter from the kernel line of your default boot you can see if it loads and possibly an error message (see /boot/grub/menu.lst).

**Drunken** · July 27th, 2009

I tried that, no errors from what I can see, there was no splash anyway I don't think.

Also, after the reboot if I type I get:

Code:

root@ubuntu-raid:~# mdadm --assemble --scan --verbose
mdadm: looking for devices for further assembly
mdadm: cannot open device /dev/sdc5: Device or resource busy
mdadm: no recogniseable superblock on /dev/sdc2
mdadm: cannot open device /dev/sdc1: Device or resource busy
mdadm: cannot open device /dev/sdc: Device or resource busy
mdadm: no RAID superblock on /dev/sdb
mdadm: cannot open device /dev/sda1: Device or resource busy
mdadm: cannot open device /dev/sda: Device or resource busy
mdadm: /dev/sdb1 is identified as a member of /dev/md/0, slot 1.
mdadm: no uptodate device for slot 0 of /dev/md/0
mdadm: added /dev/sdb1 to /dev/md/0 as 1
mdadm: /dev/md/0 assembled from 1 drive - not enough to start the array.
mdadm: looking for devices for further assembly
mdadm: no recogniseable superblock on /dev/sdb
mdadm: No arrays found in config file or automatically

Where is the superblock supposed to be, sda1 or sdb1?
Also notice "/dev/sda1: Device or resource busy" would that mean that I failed because of that, or because it's already mounted as /dev/md/0 but just not active?

**jkcrowell** · July 28th, 2009

I had essentially the same problem, and so have others on the forum. The problem is, mdadm needs to have the /etc/mdadm/mdadm.conf file set up correctly. Some sources have said this file isn't required, but it certainly seems to be. The way to set it up correctly is:

Code:

sudo mdadm --examine --scan --config=mdadm.conf >> /etc/mdadm/mdadm.conf

See this very similar thread:

http://ubuntuforums.org/showthread.php?t=1225334

The thing which really burnt me, was that apparently other linux installations have this file located at /etc/mdadm.conf. However, Ubuntu has it in /etc/mdadm/mdadm.conf. So I'd had my file configured correctly, but in the wrong location. It didn't work that way. When I rebuilt my array and edited the correct mdadm.conf, everything was peachy.