Dne 2.9.2014 v 16:11 Timur Alperovich napsal(a):
Thanks for the reply Zdenek!
I realized that the biggest confusion for me is that I'm using LVM2 tools
2.02.98-6 (which is the latest version in Ubuntu) and the swapping support was
added in 2.02.98-9 (I'm curious why they didn't pick the latest of 2.02.98).
On Tue, Sep 2, 2014 at 2:06 AM, Zdenek Kabelac <zkabelac@redhat.com
<mailto:zkabelac@redhat.com>> wrote:
Dne 1.9.2014 v 20:13 Timur Alperovich napsal(a):
Hi there,
I'm using LVM 2.02.98 and encountered a metadata corruption issue. To
recover
from it, I attempted to perform the following steps:
1. thin_check /dev/mapper/pool_tmeta
2. thin_dump /dev/mapper/pool_tmeta > /tmp/metadata
Hi
NEVER EVER use _tmeta device from running active thin-pool volume.
It's the very same case like you would be running 'fsck' on
a mounted filesystem.
3. dd if=/dev/zero of=/dev/mapper/pool_tmeta
4. thin_restore -i /tmp/metadata -o /dev/mapper/pool_tmeta
All of the above steps have succeeded, however, when attempting to
list the
_metadata\_percent_ field, I get an error:
I'm surprised you've not got kernel OOPS after such brutal destruction
of life metadata device (i.e. almost equal to zeroing your root volume).
Is this a known issue and is there a workaround? I need to be able to
examine
the _metadata\_percent_ field to make sure we don't exhaust the
metadata space.
Normal way -
lvconvert --repair vg/pool
I believe this was added in 2.02.102. Unfortunately, upgrading LVM2 is a bit
tricky on Ubuntu (will need to build the package from source).
If this is not working - then you can 'swap' metadata out of your thin-pool
using following sequence-
- make sure pool is not active.
- build temporary local LV (lvcreate -l1 vg -n temp)
- swap this LV with metadata of to-be-repaired pool
(lvconvert --thinpool vg/fixpool --poolmetadata temp)
This command fails, as --poolmetadata is not a valid option. I found that the
swapping was not supported until 2.02.98-9 and I'm using 2.02.98-6 (in
2.02.98-9 changelog: "Add lvconvert support to swap thin pool metadata
volume."). Is there a way to do this without the swapping support? I guess I
should be able to do it with dmsetup? I'm not sure how painful that would be.
I'll look into upgrading the version, as well (which is probably the right
thing to do).
IMHO by far the compilation of upstream git repo is the simplest way how
to do it - everything else is much much more complicated.
You could probably active thin-pool - and via dmsetup remove running pool
target - which should left active _tmeta device - and then you should be able
to play with this - thought it will be very tricky to not make a mistake
with this type of work.
Zdenek
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