[linux-lvm] how to recover after thin pool metadata did fill up?

[Zdenek Kabelac]

Dne 17.10.2012 22:21, Andres Toomsalu napsal(a):
> Hi,
>
> I'm aware that thin provisioning is not yet production ready (no metadata resize) - but is there a way to recover from thin pool failure when pool metadata was filled up?
>
> I did setup 1.95T thin pool and after some usage pool metadata (128MB) was filling up to 99,08% - so all pool thin volumes went into read-only state.
> Problem is that I cannot find a way in order to recover from this failure - eg also unable to delete/erase thin volumes and pool - only option seems to be full disk PV re-creation (eg OS re-install).
>
> Is there a way to recover or delete thin pool/volumes - without erasing other (normal) LVs in this Volume Group?
> For example dmsetup remove didn't help.
>
> Some diagnostic output:
>
> lvs -a -o+metadata_percent
>    dm_report_object: report function failed for field data_percent
>    --- REPEATABLE MSG ---
>    dm_report_object: report function failed for field data_percent
>    LV                       VG         Attr     LSize   Pool Origin       Data%  Move Log Copy%  Convert Meta%
>    pool                     VolGroupL0 twi-i-tz   1,95t                    75,28                          99,08
>    [pool_tdata]             VolGroupL0 Twi-aot-   1,95t
>    [pool_tmeta]             VolGroupL0 ewi-aot- 128,00m
>    root                     VolGroupL0 -wi-ao--  10,00g
>    swap                     VolGroupL0 -wi-ao--  16,00g
>    thin_backup              VolGroupL0 Vwi-i-tz 700,00g pool
>    thin_storage             VolGroupL0 Vwi---tz 900,00g pool
>    thin_storage-snapshot1   VolGroupL0 Vwi-i-tz 700,00g pool thin_storage
>    thin_storage-snapshot106 VolGroupL0 Vwi-i-tz 900,00g pool thin_storage
>    thin_storage-snapshot130 VolGroupL0 Vwi-i-tz 900,00g pool thin_storage
>    thin_storage-snapshot154 VolGroupL0 Vwi-i-tz 900,00g pool thin_storage
>    thin_storage-snapshot178 VolGroupL0 Vwi-i-tz 900,00g pool thin_storage
>    thin_storage-snapshot2   VolGroupL0 Vwi-i-tz 700,00g pool thin_storage
>    thin_storage-snapshot202 VolGroupL0 Vwi-i-tz 900,00g pool thin_storage
>
> dmsetup table
> VolGroupL0-thin_storage--snapshot2:
> VolGroupL0-thin_storage--snapshot178:
> VolGroupL0-swap: 0 33554432 linear 8:2 41945088
> VolGroupL0-thin_storage--snapshot1:
> VolGroupL0-root: 0 20971520 linear 8:2 20973568
> VolGroupL0-thin_storage--snapshot130:
> VolGroupL0-pool:
> VolGroupL0-thin_backup:
> VolGroupL0-thin_storage--snapshot106:
> VolGroupL0-thin_storage--snapshot154:
> VolGroupL0-pool-tpool: 0 4194304000 thin-pool 253:2 253:3 1024 0 0
> VolGroupL0-pool_tdata: 0 2097152000 linear 8:2 75499520
> VolGroupL0-pool_tdata: 2097152000 2097152000 linear 8:2 2172913664
> VolGroupL0-pool_tmeta: 0 262144 linear 8:2 2172651520
> VolGroupL0-thin_storage--snapshot202:
>
> lvremove -f VolGroupL0/pool
>    Thin pool transaction_id=640, while expected: 643.
>    Unable to deactivate open VolGroupL0-pool_tdata (253:3)
>    Unable to deactivate open VolGroupL0-pool_tmeta (253:2)
>    Failed to deactivate VolGroupL0-pool-tpool
>    Failed to resume pool.
>    Failed to update thin pool pool.
>


Unfortunately there is no 'easy' advice for now yet - you hit current 
Achilles heel of thinp support in lvm2 - we are thinking how to make recovery 
usable for user - but it's not easy task since many things are making it very 
complex - so it still needs some month of work.

As for now - you would need to download git source and disable certain 
security check directly in the source to allow activation of damaged pool.

I guess I could provide you some extra patch that would allow you to active 
thin pool in 'read-only' mode (but it's not yet ready for upstream).

Thus you should be able access 'some' data in this mode with a big note - 
since devices would be in read-only mode - you cannot even run  fsck on such 
partition - and since you have transaction_id mismatch - it would need
some analysis to see what actually happened - are you able to provide me
archive files for the history of your recent lvm commands -
it should not allow you to have difference bigger then 1 - so there is 
probably some bug (unless you are using some old version of lvm2 with initial 
thinp support)

Zdenek