openstack team mailing list archive

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

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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