[dm-devel] Reducing size of thin spare metadata, thin metadata

[Zdenek Kabelac]

Dne 6.10.2014 v 09:59 Patrik Horník napsal(a):
> Hi,
>
> 2014-10-06 9:39 GMT+02:00 Zdenek Kabelac <zkabelac at redhat.com>:
>> Dne 6.10.2014 v 09:28 Patrik Horník napsal(a):
>>
>>> Hi,
>>>
>>> is it possible to (safely) reduce size of thin metadata and / or thin
>>> spare metadata? What size of spare metadata is needed? Can it be
>>> smaller than size of pool metadata?
>>>
>>
>> You could remove pool spare volume anytime  - lvremove.
>> (it's only used for automated lvconvert --repair)
>>
>> Repair needs free space in VG - if there is no free space - well tool can't
>> be used.
>
> when does automated lvconvert --repair kick in? Can I do it manually
> if it cannot continue automatically? (I actually have space for spare
> metadata so I want it there if it useful but smaller. I only need to
> decrease size of my volume group by couple of 100s MB because of
> moving to new device. My spare is 8 GB as is regular metadata.)

When thin-pool does not pass 'thin-check' during thin-pool activation,
you could try to use this  'lvconvert --repair' at first.

Basically it automates steps described in previous mail - except it will try 
to use bigger 'replaceable' LV.

Yet the functionality is not really any better then that - it's still missing
many validation checks between user-land lvm2 metadata and kernel-land 
thin-pool metadata.

But it's being improved.
Meanwhile any 'major' damage of thin-pool metadata do need  'hand' work repair 
- since human can do far better decision then this initial implementation.

Also note - any pool damage is still important to be reported - as
thin pool metadata should be nearly impossible to break in the first place ;)

Zdenek