[openstack-dev] [Nova] Raw vs Qcow2 images_type in nova/libvirt

Dmitry Guryanov dguryanov at parallels.com
Tue Jan 20 11:14:30 UTC 2015

On 01/19/2015 11:41 PM, Michael Still wrote:
> Mostly.
> qcow2 can do a copy on write layer, although it can be disabled IIRC.
> So if COW is turned on, you get only the delta in the instance
> directory when using qcow2.

It seems you have to set images_type=raw (or use_cow_images=false) to 
disable copy on write, image will be handled by Raw class from 

> Cheers,
> Michael
> On Tue, Jan 20, 2015 at 7:40 AM, Dmitry Guryanov
> <dguryanov at parallels.com> wrote:
>> Hello,
>> Do I understand correctly, that both Qcow2 and Raw classes in
>> libvirt/imagebackend.py can work with images in qcow2 format, but Raw copies
>> the whole base image from cache to the instance's dir and Qcow2 only creates
>> a delta (and use base image from cache)?
>> --
>> Dmitry Guryanov
>> __________________________________________________________________________
>> OpenStack Development Mailing List (not for usage questions)
>> Unsubscribe: OpenStack-dev-request at lists.openstack.org?subject:unsubscribe
>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev

Dmitry Guryanov

More information about the OpenStack-dev mailing list