[Rdo-list] Creating nova instance without backing image

[Daniel Speichert]

Hi,

In our OpenStack installation (Havana, RDO), we use Ceph as storage as
Nova, Glance and Cinder backend.

On compute nodes, instance's disks are kept on Ceph but base images are
copied from Glance (Ceph) to local disk. This works well with small
images of OS's.

However, if we upload a big image (e.g. migrating bare hardware system
to the cloud) that is only used by one instance, the image becomes the
backing file stored locally on the compute node. Here, the compute node
hit disk space limit because we expect all the data to reside on Ceph.

Is there any way to tell Nova to not use backing image for an instance?
Maybe there exists a special image property to set that tells Nova to
copy the whole image, which would put it entirely in Ceph without a
backing file?

I hope this use case makes sense for and I'd appreciate if you had any
suggestions how to resolve this issue.

Best,
Daniel