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From: Zdenek Kabelac <zdenek.kabelac@gmail.com>
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Date: Wed, 15 Jul 2015 19:51:19 +0200
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Subject: Re: [linux-lvm] Howto get real size of thinpool-snap?
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To: LVM general discussion and development <linux-lvm@redhat.com>

Dne 15.7.2015 v 14:47 Oliver Rath napsal(a):
> 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