WMCS has added Ceph to hold the images, it is not generalized yet but we can be part of the first adopters. Their high level task for now is T253365
In order to do so, we would simply need to use the flavor mediumram-ceph when creating a new instance.
It might not be doable to migrate on a per instance basis, so we might have to reprovision the instance entirely. That in turns might conflict with rebuilding the fleet to use Buster (T252071: Move all Wikimedia CI (WMCS integration project) instances from stretch to buster). Cause surely we do not want to do both changes at the same time.