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Date: Wed, 8 Sep 2010 17:38:57 +0200
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Alexander Graf <agraf@suse.de>, Avi Kivity <avi@redhat.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, qemu-devel@nongnu.org

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.