[linux-lvm] Howto get real size of thinpool-snap?

[Oliver Rath]

Hi list,

if I create a snapshot of a volume in a thinpool, first only metadata
need space. Later, through copy-on-write, the real needed size grows. Is
it possible to get this size?

Tfh!
Oliver

[Zdenek Kabelac]

Post by Oliver Rath
Hi list,
if I create a snapshot of a volume in a thinpool, first only metadata
need space. Later, through copy-on-write, the real needed size grows. Is
it possible to get this size?

When you access thin-pool kernel metadata - you could write your own tool
to parse i.e. thin_dump output and calc all info you want.

There is no 'runtime' info (since it would be quite expensive to maintain such
info all the time).

Currently lvm2 doesn't support 'life' access to running thin-pool,
but you may eventually use dmsetup message to take snapshot and access this
info runtime (since kernel target supports this).

Zdenek