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Date: Tue, 20 Aug 2013 16:51:59 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
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Subject: Re: [Qemu-devel] vmdk stream-optimised format
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To: Alex Bligh <alex@alex.org.uk>
Cc: famz@redhat.com, qemu-devel@nongnu.org

On Tue, Aug 20, 2013 at 07:51:40AM +0100, Alex Bligh wrote:
> What I'm not sure of is whether the streaming format has to be written
> sequentially from as opposed to random writes. I believe the way
> qemu-img convert works, one can't guarantee the writes are
> sequential.

It should be possible to support stream-optimized VMDK writing in
qemu-img convert.

The file format supports non-sequential layout of data - each piece of
guest data also has a logical block address with it.  You can write out
the grain table/directory at the end of the image file once you know how
data is layed out.

The VMDK spec is not great so I guess you'll also need a VMware setup to
verify your code changes.

Stefan