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Date: Wed, 15 Feb 2017 16:11:17 +0000
From: "Daniel P. Berrange" <berrange@redhat.com>
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Subject: Re: [Qemu-devel] [Qemu-discuss] Estimation of qcow2 image size
 converted from raw image
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To: Alberto Garcia <berto@igalia.com>
Cc: Nir Soffer <nsoffer@redhat.com>, Kevin Wolf <kwolf@redhat.com>, Allon Mureinik <amureini@redhat.com>, Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>, Maor Lipchuk <mlipchuk@redhat.com>, qemu-discuss@nongnu.org

On Wed, Feb 15, 2017 at 05:05:04PM +0100, Alberto Garcia wrote:
> On Wed 15 Feb 2017 04:57:12 PM CET, Nir Soffer wrote:
> >>> Let's try this syntax:
> >>>
> >>>   $ qemu-img query-max-size -f raw -O qcow2 input.raw
> >>>   1234678000
> >>>
> >>> As John explained, it is only an estimate.  But it will be a
> >>> conservative maximum.
> >>
> >> This forces you to have an input file. It would be nice to be able to
> >> get the same information by merely giving the desired capacity e.g
> >>
> >>   $ qemu-img query-max-size -O qcow2 20G
> >
> > Without a file, this will have to assume that all clusters will be
> > allocated.
> 
> ...and that there are no internal snapshots. I'm not sure if this is
> very useful in general.

As long as the caveat is documented it is fine. Internal snapshots are
often completely ignored by apps since they have many downsides compared
to using external snapshots.

Regards,
Daniel
-- 
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