[Openstack-operators] what is the different in use Qcow2 or Raw in Ceph

David Medberry openstack at medberry.net
Thu May 28 12:02:08 UTC 2015

The primary difference is the ability for CEPH to make zero byte copies.
When you use qcow2, ceph must actually create a complete copy instead of a
zero byte copy as it cannot do its own copy-on-write tricks with a qcow2

So, yes, it will work fine with qcow2 images but it won't be as performant
as it is with RAW. Also, it will actually use more of the native underlying

This is also shown as an Important Note in the CEPH docs:

On Thu, May 28, 2015 at 4:12 AM, Shake Chen <shake.chen at gmail.com> wrote:

> Hi
> Now I try to use Fuel 6.1 deploy openstack Juno, use Ceph as cinder, nova
> and glance backend.
> In Fuel document suggest if use ceph, suggest use RAW format image.
> but if I upload qcow2 image, seem working well.
> what is the different use qcow2 and RAW in Ceph?
> --
> Shake Chen
> _______________________________________________
> OpenStack-operators mailing list
> OpenStack-operators at lists.openstack.org
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators
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