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Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format


From: Anthony Liguori
Subject: Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format
Date: Wed, 08 Sep 2010 11:30:10 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.11) Gecko/20100713 Lightning/1.0b1 Thunderbird/3.0.6

On 09/08/2010 10:38 AM, Christoph Hellwig wrote:
On Wed, Sep 08, 2010 at 12:15:13PM +0100, Stefan Hajnoczi wrote:
In-place writes overwrite old data in the image file.  They do not
allocate new clusters or update any metadata.  This is why write
performance is comparable to raw in the long run.
Only if qed doesn't cause additional fragmentation.  Which it currently
does.

http://wiki.qemu.org/Features/QED/OnlineDefrag

Is a spec for a very simple approach to online defrag that I hope we can implement in the near future. I think that once we have the mechanisms to freeze clusters and to swap clusters, implementing much more sophisticated defragmentation algorithms will become easy.

Regards,

Anthony Liguori




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