[Bug 1608495] Re: IMSM fakeraid handled by mdadm: unclean mounted volumes on shutdown/reboot

[John Center]

I saw this fix & installed it before your update went out.  I did it by
hand, so I didn't know about the dracut-core package or
enabling/starting the mdadm-shutdown.service.  Even without dracut-core,
it worked for me.

I did make some changes to 64-md-raid-assembly.rules.  I commented out
the ENV{ANACONDA}=="?*", GOTO="md_inc_end" line, because I didn't think
this applied to Ubuntu.  I also made the following change:

ACTION=="add|change", IMPORT{program}="/sbin/mdadm --incremental
--export $devnode --offroot $env{DEVLINKS}"

I saw this was updated on the linux-raid list:  
[PATCH 2/4] Use correct syntax for passing DEVLINKS to mdadm from udev

I also did 2 reboots & everything seems to be working correctly.  One
question:  Does this mean that Ubuntu 18.04 will use mdadm by default
during installation instead of dmraid?

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https://bugs.launchpad.net/bugs/1608495

Title:
  IMSM fakeraid handled by mdadm: unclean mounted volumes on
  shutdown/reboot

Status in mdadm package in Ubuntu:
  Fix Committed
Status in mdadm source package in Xenial:
  Fix Committed
Status in mdadm source package in Yakkety:
  Won't Fix
Status in mdadm source package in Zesty:
  Fix Committed

Bug description:
  Opening this report for Xenial and later as this problem does surface
  again due to moving to systemd.

  Background:

  mdadm is used to create md raid volumes based on Intel Matrix Storage
  Manager fakeraid metadata. The setup usually consists of a container
  set that contains one or more raid volumes. Which is the reason that
  those fakeraid volume are more affected by timing issues on
  shutdown/reboot.

  In my specific setup I am using one of the IMSM raid volumes as a LVM
  PV and one LV of that is mounted as /home. The problem is that
  unmounting /home on shutdown/reboot will update the filesystem
  superblock which causes the raid state to become dirty for a small
  period of time. For that reason with sysvinit scripts there is a
  mdadm-waitidle script which *must* be run after the umountroot (or for
  /home at least after umountfs) script has run.

  With Xenial both umountroot and umountfs are softlinks to /dev/null in /lib/systemd/system, so I am not sure they are good to cause the mdadm-waitidle to be delayed *after* all filesystems are unmounted.
  Practically I see that if /home is mounted on shutdown/reboot, the raid set will go into a full resync the next time I boot (additional pain but different problem: the resync appears to be much more aggressive than in the past, delaying boot a lot and rendering the system barely usable until it finishes). If I manually unmount /home before the reboot, the raid set is good.

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