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Re: [RFC PATCH 0/3] qemu: Propagate cluster size to new qcow2 images



On Wed, Aug 26, 2020 at 10:32:04 -0500, Eric Blake wrote:
> On 8/26/20 9:56 AM, Peter Krempa wrote:
> > Cluster size may have performatnce implications. Propagate the cluster
> > size used by the original image to any copy or overlay.
> > 
> > Peter Krempa (3):
> >    qemu: monitor: Detect image cluster size from
> >      'query-named-block-nodes'
> >    qemu: block: Allow specifying cluster size when using
> >      'blockdev-create'
> >    qemuBlockStorageSourceCreateDetectSize: Propagate cluster size for
> >      'qcow2'
> 
> It's not as flexible as allowing the user to customize sizes, but it
> definitely makes sense and is a sane heuristic, better than adccidentally
> creating an overlay with 64k clusters atop a base image with 1M clusters.

Actually, I'll modify the condition in patch 3 to also check that the
configured cluster size in the new image is 0 before applying one from
the template image. That way it will be simpler to wire up configurable
cluster size by just dealing with the XML.

> 
> Series:
> Reviewed-by: Eric Blake <eblake redhat com>

Thanks I'll push it soon.


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