This is a historical weirdness. I think we should consider cleaning up -- ceph is special cased as a config drive store compared to other backends. IIRC this happened because back then we expected the config drives to mostly be on shared storage, but then ceph turned up and broke that assumption.

Specifically, https://github.com/openstack/nova/blob/master/nova/virt/libvirt/driver.py#L5451 onwards calls https://github.com/openstack/nova/blob/master/nova/virt/libvirt/imagebackend.py#L1164 which imports the image and then cleans up the temporary local copy. For reference this code was added in https://review.opendev.org/c/openstack/nova/+/123073 as a response to https://review.opendev.org/c/openstack/nova/+/214773 being blocked from merging and me feeling guilty about that.

The place I think this is especially weird right now is that if your instance has all its disks on cinder, and you add a config drive, then suddenly live migration might need to do a streamed block migration just for the config drive, which doesn't seem great.

The obvious alternative is to have config drives in cinder. How would people feel about config drives being very small cinder volumes instead of a special case? Is there a better thing we could be doing here?

If we could agree on a scope for what we think we should do here I'd be willing to consider if I have the time to take a swing at it.

On Fri, 28 Feb 2025, 7:03 am Pardhiv Karri, <meher4india@gmail.com> wrote:

Hi Sean,
Thank you for the quick response. We recently moved the backend storage from Ceph to PureStorage. Now all the instance disks are in PureStorage but the config drives are in Ceph. For just a few single digit GB we need to maintain the entire Ceph cluster. So decided to completely get rid of these drives and Ceph.

Thanks,
IM

On Thu, Feb 27, 2025 at 11:58 AM Sean Mooney <smooney@redhat.com> wrote:

On 27/02/2025 19:18, Pardhiv Karri wrote:
> Hi,
>
> We are on the Openstack Queens version. We added the config drive
> option during its build but never used it. How can we remove it? The
> "OpenStack server delete --no-config-drive" option isn't available due
> to the older version we are using. What is the best way to eliminate
> it, hopefully without rebooting the instances?

we do not support changing this durign the lifetime of an instnace

you coudl hack the db but that the only option

im not sure why you want to remove it?

>
> Thanks,
> IM
>
>
>