[Bug 1651838] Re: bootup halted, lvms NOT active, one LV lost

[Gerben]

Hi,

I know what is going on: there is some kind of a replay of the snapshot
being performed when booting. This results into increasing boot times on
increasing snapshot allocation.

I've tested this with a virtual client with incremental blocks changed
on a LV which being the source of a snapshot LV. Upon bootup I could
detect incremental blocks read on the snapshot COW LV (the largest user)
(log the results of iostat in /etc/rc.local).

When switching off caching on the client disk I could indeed detect
incremental boot times with incremental blocks changed. This up to a
point where the boot process stalls due to a timeout requiring manual
intervention. (snapshot replay continues in the background).

When in a good state a replay of the snapshot should not be required (in
my opinion). I guess some kind of journaling is going on within LVM2,
requiring at most the last (couple of) transaction(s) on a snapshot to
be replayed, not the complete snapshot.

This may need to be reported upstream (which I will do when no other
comments here).

Greetings,

Gerben

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https://bugs.launchpad.net/bugs/1651838

Title:
  bootup halted, lvms NOT active, one LV lost

Status in lvm2 package in Ubuntu:
  New

Bug description:
  Hi,

  The bootup process is stopping in 'emergency mode', I have to manually
  intervene and perform a 'vgchange -a y' and after 3.5 minutes 6
  logical volumes are active (however I do have 7). Only then I can
  finalize the boot process.

  Subsequent (all) boots I have to intervene. lvdisplay fails to show
  one logical volume, which is shown under /dev/mapper. This volume is
  not used, just contained some offline data.

  I also had an unplanned reboot a few days ago on the machine without
  having it under a load. The lost LV was not in use at that time (has
  not been mounted for a long time).

  I've got one snapshot defined, which acts as a mirror (LV Size same as
  origin), with only 4.31 % allocated to that snapshot.

  When viewing the system with a live desktop only the 'cow' LV is shown
  under /dev/mapper, none of the other LV's.

  Why is this unused LV lost?

  The data on the 'lost' LV is not needed at the moment. I'll leave
  things 'as is' for the moment for investigation.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: lvm2 2.02.133-1ubuntu10
  ProcVersionSignature: Ubuntu 4.4.0-57.78-generic 4.4.35
  Uname: Linux 4.4.0-57-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.4
  Architecture: amd64
  Date: Wed Dec 21 19:25:22 2016
  InstallationDate: Installed on 2016-06-01 (202 days ago)
  InstallationMedia: Ubuntu-Server 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.3)
  ProcEnviron:
   LANGUAGE=en_US:en
   TERM=xterm
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: lvm2
  UpgradeStatus: No upgrade log present (probably fresh install)

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