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

[Zdenek Kabelac]

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.

You could also reduce size of thin pool metadata in case it's too big, just 
not online.


With offline thinpool with these manual steps
(will be later automated with tool as well):

--

make a temporary LV of any size.
swap this temp LV with  pool metadata

# lvconvert --thinpool  vg/mypool   --poolmetadata mytemplv

Create your volume for metadata with new reduced size
(unsure which size is your target - but some calcs based on estimated usage 
are necessary)

Activate   mytemplv  which has now real metadata from thinpool.

# thin_repair  -i /dev/vg/mytemplv   -o /dev/vg/mynewsizemeta

# thin_check  /dev/vg/mynewsizemeta


If all is green - swap new meta into your thinpool

# lvconvert --thinpool  vg/mypool   --poolmetadata mynewsizemeta


If all works great you are done :)
In all other cases you have your backup at hand :)

Yeah - you still have old metadata in mytemplv - this volume you may remove
later if all works well - otherwise you may try to swap this volume back.

Zdenek