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[William Herry <william.herry.china@xxxxxxxxx>]

so, what changes should I make if I want use raw in openstack, I didn't
find some configure option in nova.conf.sample

I also try to modify the source code in nova/virt/libvirt/utils.py, and
didn't succeed

I noticed that the type of snapshot is same as the instance's image by
default, does this right, and what about the type of model image that
uploaded to glance, does it affect the disk type I use?

Thanks

On Tue, Apr 17, 2012 at 4:41 PM, Daniel P. Berrange <berrange@xxxxxxxxxx>wrote:

> On Tue, Apr 17, 2012 at 04:23:04PM +0800, William Herry wrote:
> > Hi all
> >
> > we plan to use openstack on our production,
> > we are not sure which disk type will be the better choice
> >
> > I did a little test on qcow2 and it's performance looks good when I use
> > cache=writeback
> >
> > can some one give us some advice, or some article,
> > cause for such common topic must be discussed before
>
> Raw files or block devices will always have some performance advantage
> over qcow2, though I don't have figures to tell you just how much of
> a difference it will be. The performance gap is certainly much smaller
> than it used to be a few years back.
>
> The more important question is probably, do you actually need any of
> the other features that qcow2 gives over raw ? eg internal snapshots,
> external backing files, encryption, compression, etc ?  If you don't
> need any of these features, then there is no real point in choosing
> to use qcow2 over raw.
>
> REgards,
> Daniel
> --
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>



-- 

===========================
William Herry

WilliamHerryChina@xxxxxxxxx