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Re: [Qemu-devel] qmp drive-mirror vs qemu-img convert , drive-mirror rea
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] qmp drive-mirror vs qemu-img convert , drive-mirror really slow |
Date: |
Mon, 21 Jan 2013 11:35:40 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 |
Il 21/01/2013 10:40, Alexandre DERUMIER ha scritto:
> Hi list,
>
> I'm doing some speed benchmark between
>
> drive-mirror vs qemu-img convert ,
>
> and drive-mirror seem to be a lot slower.
>
>
> test:
>
> convert 1 32GB qcow2 file to raw file, local storage (6 disk 15k in raid10 +
> raid BBU cache)
>
> time result:
>
> qemu-img : 30sec
> drive-mirror (vm is paused, no writes) : 5min
>
>
> Any idea why drive-mirror is so slow ? (maybe does it use directsync when
> mirroring ?)
No, it doesn't. Probably it's because the image is sparse? The current
code in git master has a very coarse granularity (1 MB).
Please try the blkmirror-job-1.4 branch from my github repo
(git://github.com/bonzini/qemu.git). That branch uses the qcow2 file's
cluster size as the granularity, and has other optimizations that kick
in when the image is sparse.
Paolo
> I think both should have around same speed ?
>
>
> Best Regards,
>
> Derumier Alexandre
>
>
>