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

[Stefan Bader]

I did a quick test and created a mdadm.shutdown in /lib/systemd/system-
shutdown like the template in Yakkety (adapted path to binary and made
it executable). Unfortunately that did not help. However there might be
some step missing to activate it in systemd. I guess I need to make
output more verbose and add some delay to be sure that this indeed is
executed and when.

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

Status in mdadm package in Ubuntu:
  New

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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