[Bug 1681244] [NEW] mdadm fails to assemble IMSM - Cannot assemble mbr metadata on /dev/md126

[François]

Public bug reported:

/* General Description
******************************************************/

I'm having a problem using mdadm in a "fakeraid IMSM" environment.  It
seems like the container Volume0_0 is found and assembled but the
partitions (x3) are never put together.  The setup works properly when
manually using a mix of dmraid for IMSM and mdadm for my other RAID1
regular linux software raid devices.


/* System *******************************************************************/

Ubuntu 16.10
mdadm 3.4-4


/* Debug Information ********************************************************/

Please consider the following debug trace during initramfs boot up:

/dev/sdb is identified as a member of /dev/md/imsm0, slot -1.
/dev/sda is identified as a member of /dev/md/imsm0, slot -1.
added /dev/sda to /dev/md/imsm0 as -1
added /dev/sdb to /dev/md/imsm0 as -1
Container /dev/md/imsm0 has been assembled with 2 drives
looking for devices for further assembly
[...]
looking in container /dev/md/imsm0
found match on member /md127/0 in /dev/md/imsm0
Started /dev/md/Volume0_0 with 2 devices
looking for devices for further assembly
[...]
looking in container /dev/md/imsm0
member /md127/0 in /dev/md/imsm0 is already assembled
looking for devices for further assembly
[...]
looking for devices for further assembly
Cannot assemble mbr metadata on /dev/md126
[...]

Addtionnal info : GParted is complaining that "Not all of the space
available to /dev/sda appears to be used, you can fix the GPT to use all
of the space (an extra 50016680 blocks) or continue with the current
setting?", and I also click ignore.  Same applies for /dev/sdb.


/* Disks information ********************************************************/

IMSM RAID1 on /dev/sda and /dev/sdb SSDs (GPT with protective MBR)

DMRAID output (working, for reference only)

isw_hggicbcjd_Volume0
- isw_hggicbcjd_Volume0p1 - mounted on /boot/efi - vfat
- isw_hggicbcjd_Volume0p2 - mounted on /boot - ext4
- isw_hggicbcjd_Volume0p3 - mounted on / - LVM on luks


/* Workaround ***************************************************************/

To boot my system, I go through these steps to fallback on dmraid :
kernel option break=mount

from initramfs prompt
- mdadm --stop /dev/md126
- mdadm --stop /dev/md127
- dmraid -ay
- cryptsetup luksOpen /dev/mappper/isw_hggicbcjd_Volume0p3 isw_hggicbcjd_Volume0p3_crypt
- CTRL-D


##############################################################################
INITIALLY REPORTED HERE
https://ubuntuforums.org/showthread.php?t=2353942

** Affects: mdadm (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: imsm

** Attachment added: "Photo of the debug output"
   https://bugs.launchpad.net/bugs/1681244/+attachment/4859078/+files/mdadm.jpg

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https://bugs.launchpad.net/bugs/1681244

Title:
  mdadm fails to assemble IMSM - Cannot assemble mbr metadata on
  /dev/md126

Status in mdadm package in Ubuntu:
  New

Bug description:
  /* General Description
  ******************************************************/

  I'm having a problem using mdadm in a "fakeraid IMSM" environment.  It
  seems like the container Volume0_0 is found and assembled but the
  partitions (x3) are never put together.  The setup works properly when
  manually using a mix of dmraid for IMSM and mdadm for my other RAID1
  regular linux software raid devices.

  
  /* System *******************************************************************/

  Ubuntu 16.10
  mdadm 3.4-4

  
  /* Debug Information ********************************************************/

  Please consider the following debug trace during initramfs boot up:

  /dev/sdb is identified as a member of /dev/md/imsm0, slot -1.
  /dev/sda is identified as a member of /dev/md/imsm0, slot -1.
  added /dev/sda to /dev/md/imsm0 as -1
  added /dev/sdb to /dev/md/imsm0 as -1
  Container /dev/md/imsm0 has been assembled with 2 drives
  looking for devices for further assembly
  [...]
  looking in container /dev/md/imsm0
  found match on member /md127/0 in /dev/md/imsm0
  Started /dev/md/Volume0_0 with 2 devices
  looking for devices for further assembly
  [...]
  looking in container /dev/md/imsm0
  member /md127/0 in /dev/md/imsm0 is already assembled
  looking for devices for further assembly
  [...]
  looking for devices for further assembly
  Cannot assemble mbr metadata on /dev/md126
  [...]

  Addtionnal info : GParted is complaining that "Not all of the space
  available to /dev/sda appears to be used, you can fix the GPT to use
  all of the space (an extra 50016680 blocks) or continue with the
  current setting?", and I also click ignore.  Same applies for
  /dev/sdb.

  
  /* Disks information ********************************************************/

  IMSM RAID1 on /dev/sda and /dev/sdb SSDs (GPT with protective MBR)

  DMRAID output (working, for reference only)

  isw_hggicbcjd_Volume0
  - isw_hggicbcjd_Volume0p1 - mounted on /boot/efi - vfat
  - isw_hggicbcjd_Volume0p2 - mounted on /boot - ext4
  - isw_hggicbcjd_Volume0p3 - mounted on / - LVM on luks

  
  /* Workaround ***************************************************************/

  To boot my system, I go through these steps to fallback on dmraid :
  kernel option break=mount

  from initramfs prompt
  - mdadm --stop /dev/md126
  - mdadm --stop /dev/md127
  - dmraid -ay
  - cryptsetup luksOpen /dev/mappper/isw_hggicbcjd_Volume0p3 isw_hggicbcjd_Volume0p3_crypt
  - CTRL-D

  
  ##############################################################################
  INITIALLY REPORTED HERE
  https://ubuntuforums.org/showthread.php?t=2353942

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