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From: Eric Blake <eblake@redhat.com>
To: Max Reitz <mreitz@redhat.com>, Ivan Ren <renyime@gmail.com>,
	qemu-devel@nongnu.org
Cc: kwolf@redhat.com, qemu-block@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] qemu-img: return allocated size for block device with qcow2 format
Date: Wed, 2 May 2018 10:19:03 -0500	[thread overview]
Message-ID: <4ca76bd5-4b9a-636f-aa64-4f1aa02de4cf@redhat.com> (raw)
In-Reply-To: <34320941-dbea-8499-d342-7df967e4c23f@redhat.com>

On 05/02/2018 10:13 AM, Max Reitz wrote:

>> We also recently added 'qemu-img measure', which DOES report how many
>> clusters are in use.  Is any of that reusable here?
> 
> It only tells you that information for a hypothetical new image, though,
> doesn't it?

It has two uses: with just a size, estimate the overhead needed to 
create a file with the given format and exposing the given size to the 
guest (both sparse and fully allocated sizes are estimated); and with a 
pre-existing image, compute the exact overhead needed for 'qemu-img 
convert' to create a new image with the given format and the same 
guest-visible contents.  The latter use, where it uses an existing guest 
image as the starting point to measure, indeed only tells you what a 
hypothetical new image will occupy (the used cluster count, not the 
wr_highest_offset count) - but isn't that what you want?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

  reply	other threads:[~2018-05-02 15:19 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-02 13:34 [Qemu-devel] [PATCH] qemu-img: return allocated size for block device with qcow2 format Ivan Ren
2018-05-02 14:02 ` Eric Blake
2018-05-03 13:06   ` 叶残风
2018-05-04 14:35     ` Max Reitz
2018-05-04 15:57       ` Ivan Ren
2018-05-02 14:37 ` Max Reitz
2018-05-02 15:01   ` Eric Blake
2018-05-02 15:13     ` Max Reitz
2018-05-02 15:19       ` Eric Blake [this message]
2018-05-02 15:33         ` Max Reitz
2018-05-03 13:08   ` 叶残风
2018-05-04 14:27     ` Max Reitz

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