[Bug 942106] Re: software raid doesn't assemble before mount on boot

[Josh Bendavid]

Hi,
This fix does not work for me.  I have a system with a single md raid 5 array with 5 disks, and root on a seperate non-raid disk.  With the default bootdegraded=false my system frequently drops to the initramfs prompt with the usual timed out message.  With BOOT_DEGRADED=true set in the mdadm initramfs config, the system frequently drops to the initramfs prompt complaining of 2 of 5,  3 of 5, or 4 of 5 disks failed to be added to the array.

I was able to fix the problem by horrible hack by adding a hard sleep after the udevadm settle call in wait_for_udev
(in /usr/share/initramfs-tools/scripts/functions)
# Wait for queued kernel/udev events
wait_for_udev()
{
        command -v udevadm >/dev/null 2>&1 || return 0
        udevadm settle ${1:+--timeout=$1}
        sleep 15
}

With this change the system reliably boots (albeit slightly slower).
with the raid properly detected with all 5 drives.

This suggests to me that udevadm settle is not doing what it's supposed
to be doing (waiting for the relevant controller/drives to fully come
up.)

I am running Ubuntu 13.10 on an Asus M2N-E Motherboard with 6 disks
attached to the onboard sata ports.  (One with the root partition and
the other 5 as part of the raid 5 array).

This board runs an older AMD-based Nvidia chipset and does not support
ahci, so the sata drives run through the sata_nv module.

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https://bugs.launchpad.net/bugs/942106

Title:
  software raid doesn't assemble before mount on boot

Status in “mdadm” package in Ubuntu:
  Fix Released
Status in “update-manager” package in Ubuntu:
  Fix Released
Status in “mdadm” source package in Precise:
  Fix Released
Status in “update-manager” source package in Precise:
  Fix Released
Status in “mdadm” source package in Quantal:
  Fix Released
Status in “update-manager” source package in Quantal:
  Fix Released

Bug description:
  [IMPACT]

   * Due to small time-outs udev may not detect all attached drives
  quick enough to be processed and assembled into a RAID array

  * This results in dropping a user into an initramfs shell or if
  BOOT_DEGRADED is set the boot will proceed degrading RAID unnecessary

   * The fix is to include wait_for_udev call to give udev more time to
  find the drives which are part of RAID

  [TESTCASE]

   * Install RAID preferably with a "slow" interface, e.g. RAID1 with
  one drive on external USB

  * Reboot multiple times and notice that sometimes boot fails

  * Upgrade to the -proposed package

  * Reboot multiple times and notice that boot fail less often

  [Regression Potential]

  * boot speed is decreased due to the nature of the fix, i.e. adding a physical delay
  * Multiple reports in this bug and on the ubuntuforums reporting that this change "fixes" the boot issue for the users

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