[Bug 1556602] Re: LVM cannot mount LVM Cached Volumes from LMDE Betsy

[Guy Thouret]

As I understand it, this bug affects any cached volumes created using
the lvm2 package from 15.10 and then attempting to mount that volume
under 16.04.

I have this issue on two machines.  As a workaroundon one of the
machines I was able to mount the volume after booting into a 15.10 live
environment, converting the lvs back to uncached volumes, booting back
to 16.04 and converting to cached volumes again.

Looking at the Fedora bug report this is caused by new cache metadata
attributes missing in the metadata of volumes created using previous
lvm2 version.  A patch exists that adds default attributes to the cache
metadata if they don't already exists and this will resolve the issue.

Link to patch: https://www.redhat.com/archives/lvm-
devel/2015-November/msg00098.html

I'll check upstream to see if a bugreport exists for this lvm2 package.

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Title:
  LVM cannot mount LVM Cached Volumes from LMDE Betsy

Status in lvm2 package in Ubuntu:
  Confirmed

Bug description:
  I'm test driving Ubuntu Mate Beta 1 (from USB) on a machine that uses
  LVM caching. (I use some SSD to cache old hard drives). My LVM setup
  was created with Linux Mint Debian Edition - Betsy release.

  The system cannot mount these cached volumes due to the following
  error reported by 'pvs':

  ubuntu-mate at ubuntu-mate:~$ sudo pvs
    LV CacheArchive has invalid cache's feature flag.
    LV CacheArchive is missing cache policy name.
    Internal error: LV segments corrupted in CacheArchive.
    LV CacheArchive has invalid cache's feature flag.
    LV CacheArchive is missing cache policy name.
    Internal error: LV segments corrupted in CacheArchive.
    PV         VG   Fmt  Attr PSize   PFree 
    /dev/sda5  vga  lvm2 a--   80.00g 70.00g
    /dev/sda6  vga  lvm2 a--  160.00g 50.00g
    /dev/sdb1  vga  lvm2 a--  200.00g 50.00g

  I did a bit of googling and found a similar report for upgrades from
  Fedora 21 to Fedora 23. See
  https://bugzilla.redhat.com/show_bug.cgi?id=1282188.

  I'll annotate this bug with the LVM version from my existing Debian
  based configuration in a few minutes.

  This is a show-stopper for me because I use LVM caching on both of my
  PCs. It's a great way to marry a 256 GB SSD with a 2 TB hard drive. I
  keep the OS and some key partitions on the SSD and then use the rest
  of the SSD to cache the hard drive.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: lvm2 2.02.133-1ubuntu7
  ProcVersionSignature: Ubuntu 4.4.0-7.22-generic 4.4.2
  Uname: Linux 4.4.0-7-generic x86_64
  ApportVersion: 2.20-0ubuntu3
  Architecture: amd64
  CasperVersion: 1.367
  CurrentDesktop: MATE
  Date: Sun Mar 13 12:48:41 2016
  LiveMediaBuild: Ubuntu-MATE 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160224)
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: lvm2
  UpgradeStatus: No upgrade log present (probably fresh install)

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