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From Edison Su <Edison...@citrix.com>
Subject RE: qemu-img convert a qcow2 to a qcow2
Date Wed, 05 Dec 2012 21:29:49 GMT
If the source image has dependence on other images, then we should use "qemu-img convert ",
otherwise, "cp" is enough. 

> -----Original Message-----
> From: Marcus Sorensen [mailto:shadowsor@gmail.com]
> Sent: Wednesday, December 05, 2012 1:01 PM
> To: cloudstack-dev@incubator.apache.org
> Subject: Re: qemu-img convert a qcow2 to a qcow2
> 
> Eventually we'll probably want to support multiple versions, replacing one or
> both of the formats with variables, but even then we'll probably just want to
> copy if source format == destination format.
> 
> 
> On Wed, Dec 5, 2012 at 1:51 PM, Rohit Yadav <rohit.yadav@citrix.com>
> wrote:
> 
> >
> > On 05-Dec-2012, at 12:17 PM, Marcus Sorensen <shadowsor@gmail.com>
> wrote:
> >
> > > Anyone know why we do a convert from qcow2 to qcow2 when we crete
> a
> > volume
> > > or template? It seems slower than file copy, and it strips valuable
> > > compression which could speed up deployments significantly. Our
> > > qcow2 templates are compressed to about 1/3 size of uncompressed,
> > > and since the compression is read-only it doesn't really affect
> > > future write
> > performance,
> > > and gives a slight performance gain to reads since less is read.
> > >
> > > createvolume.sh
> > > qemu_img convert -f qcow2 -O qcow2
> > >
> > > managesnapshot.sh
> > > qemu_img convert -f qcow2 -O qcow2
> > >
> > > createtmplt.sh
> > > qemu_img convert -f qcow2 -O qcow2
> > >
> > > I'd suggest if we already know it's qcow2, and we want to create a
> > > qcow2
> > to
> > > copy the file. Objections?
> >
> >
> > I don't know why we do that, but what the command is saying is that we
> > want to convert an input image from qcow2 to keeping the same output
> > format, -O qcow2 But yes, if the input format is already qcow2 and
> > output is qcow2 we can just copy the file. Edison?
> >
> > Regards.

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