[Bug 682019] Re: incorrect RAID assembly when multiple drives specified in initramfs mdadm.conf

[Jean-Philippe Guérard]

*** This bug is a duplicate of bug 942106 ***
    https://bugs.launchpad.net/bugs/942106

** This bug is no longer a duplicate of bug 683476
   Software raid intermittently fails to start at boot time
** This bug has been marked a duplicate of bug 942106
   mdadm-functions missing udevadm settle (?)

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https://bugs.launchpad.net/bugs/682019

Title:
  incorrect RAID assembly when multiple drives specified in initramfs
  mdadm.conf

Status in “mdadm” package in Ubuntu:
  New

Bug description:
  Binary package hint: mdadm

  I have a ubuntu 10.04.1 (i386 server) system with 4 mdadm devices,
  which is a mixture of raid0 and raid1. The primary boot partition is
  on md0, which is raid1.

  md0 -> /dev/sda1, /dev/sdb1 (raid1, mounted  at "/" )
  md1 -> /dev/sda2, /dev/sdb2 (raid0, swap)
  md2 -> /dev/sda3, /dev/sdb3 (raid1, mounted at "/home")
  md3 -> /dev/sda4, /dev/sdb4 (raid0, mounted at "/home/pub/unmirrored")

  grub is installed on both /dev/sda and /dev/sdb.

  (Yes, I know I could have done two RAID devices with two partitions in
  each, but that also caused the problem that I am about to explain)

  The bug, as it seems, occurs when I specify ALL 4 drives in mdadm.conf
  inside the initramfs image. If I specify only md0 in initramfs, and
  all 4 drives in /etc/mdadm/mdadm.conf (on md0), the machine boots
  perfectly. However, the machine will not boot if I specify only one
  drive in both .conf files, or all 4 drives in both .conf files.

  This means that each time a new kernel is installed, update-initramfs
  creates a new image which does not boot (because it uses
  /etc/mdadm/mdadm.conf from md0 in the image).

  Here's the scary part: When I specify all 4 drives in initramfs, the
  machine drops into an initramfs shell at boot. When I inspect the
  assembled drives, it has created md3 as raid 0 using /dev/sda and
  /dev/sdb. It has also created md0p1, md0p2 and md0p3. NONE of this is
  consistent with the superblock (mdadm --examine --scan looks fine), or
  what is in any mdadm.conf file. Also, none of these devices actually
  work.

  For the machine to recover, I need to "mdadm --delete /dev/md3", and
  then "mdadm --assemble --scan" then hit CTRL+D to continue booting.

  You'll also find that when multiple mdadm devices are specified during
  installation (alternate installer), the machine will not boot
  immediately afterwards do to this bug. I had to manually stop all but
  md0 between partitioning and installing the bootloader, then re-adding
  them to mdadm.conf after installation. This effectively created an
  initramfs with only one mdadm device (md0) in it.

  # 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 (generated with "mdadm --examine --scan")
  ARRAY /dev/md0 level=raid1 num-devices=2 UUID=6e262a6c:792ac6e6:7937b5e2:5bb6f333

  #NOTE: The following lines have to be removed from the initramfs image to boot:
  ARRAY /dev/md1 level=raid0 num-devices=2 UUID=d9cec93e:db673bd8:a0a0eea7:e933aaa5
  ARRAY /dev/md2 level=raid1 num-devices=2 UUID=9545533d:d5a2efc6:a0a0eea7:e933aaa5
  ARRAY /dev/md3 level=raid0 num-devices=2 UUID=110a8882:ee7facf4:a0a0eea7:e933aaa5

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