Re: IMSM Raid 5 always read only and gone after reboot

[Iwan Zarembo <iwan@zarembo.de>]

Hi Everyone,
Nothing worked with the last mail, so I tried it again. A different 
approach.
What I tried again:

1. I stopped and deleted the array using:
mdadm --stop /dev/md126
mdadm --stop /dev/md127
mdadm --remove /dev/md127
mdadm --zero-superblock /dev/sdb
mdadm --zero-superblock /dev/sdc
mdadm --zero-superblock /dev/sdd
mdadm --zero-superblock /dev/sde

2. I deleted all data (including partition table) on every HDD:
dd if=/dev/zero of=/dev/sd[b-e] bs=512 count=1

3. Checked if mdadm --assemble --scan can find any arrays, but I did not 
find anything.

4. I created the array again using 
https://raid.wiki.kernel.org/index.php/RAID_setup#External_Metadata
mdadm --create --verbose /dev/md/imsm /dev/sd[b-e] --raid-devices 4 
--metadata=imsm
mdadm --create --verbose /dev/md/raid /dev/md/imsm --raid-devices 4 
--level 5

The new Array did not have any partitions, since I deleted everything. 
So everything looks good.
The details are:
# mdadm -D /dev/md127
/dev/md127:
         Version : imsm
      Raid Level : container
   Total Devices : 4

Working Devices : 4


            UUID : 790217ac:df4a8367:7892aaab:b822d6eb
   Member Arrays :

     Number   Major   Minor   RaidDevice

        0       8       16        -        /dev/sdb
        1       8       32        -        /dev/sdc
        2       8       48        -        /dev/sdd
        3       8       64        -        /dev/sde

# mdadm -D /dev/md126
/dev/md126:
       Container : /dev/md/imsm, member 0
      Raid Level : raid5
      Array Size : 2930280448 (2794.53 GiB 3000.61 GB)
   Used Dev Size : 976760320 (931.51 GiB 1000.20 GB)
    Raid Devices : 4
   Total Devices : 4

           State : clean
  Active Devices : 4
Working Devices : 4
  Failed Devices : 0
   Spare Devices : 0

          Layout : left-asymmetric
      Chunk Size : 128K


            UUID : 4ebb43fd:6327cb4e:2506b1d3:572e774e
     Number   Major   Minor   RaidDevice State
        0       8       48        0      active sync   /dev/sdd
        1       8       32        1      active sync   /dev/sdc
        2       8       16        2      active sync   /dev/sdb
        3       8       64        3      active sync   /dev/sde

# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] 
[raid4] [raid10]
md126 : active (read-only) raid5 sde[3] sdb[2] sdc[1] sdd[0]
       2930280448 blocks super external:/md127/0 level 5, 128k chunk, 
algorithm 0 [4/4] [UUUU]
           resync=PENDING

md127 : inactive sde[3](S) sdd[2](S) sdc[1](S) sdb[0](S)
       836 blocks super external:imsm

unused devices: <none>

Then I stored the configuration of the array using the command
mdadm --examine --scan >> /etc/mdadm.conf

5. I used dpkg-reconfigure mdadm to make sure mdadm starts properly at 
boot time.

6. I rebooted and checked if the array was created in BIOS of the Intel 
raid.
Yes it is existing, and it looks good there.

7. I still cannot see the created array. But in palimpsest I see that my 
four hard drives are a part of a raid.

I also checked the logs for any strange entries, but no success :S

9. I used mdadm --assemble --scan to see the array in palimpsest

10. Started sync process using command from 
http://linuxmonk.ch/trac/wiki/LinuxMonk/Sysadmin/SoftwareRAID#CheckRAIDstate

#echo active > /sys/block/md126/md/array_state

#cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] 
[raid4] [raid10]
md126 : active raid5 sdd[3] sdc[2] sdb[1] sde[0]
       2930280448 blocks super external:/md127/0 level 5, 128k chunk, 
algorithm 0 [4/4] [UUUU]
       [>....................]  resync =  0.9% (9029760/976760320) 
finish=151.7min speed=106260K/sec

The problem is that the raid was gone after a restart. So I did step 9 
and 10 again.

11. Then I started to create a gtp partition table with parted.
Unfortunately mktable gpt on device /dev/md/raid (or the target of the 
link /dev/md126) never came back. Even after a few hours.

I really do not know what else I need to do to get the raid working. Can 
someone help me? I do not think I am the first person having trouble 
with it :S

Kind Regards,

Iwan