storage_hosts:
      controller1:
        ip: 172.29.236.10
        container_vars:
          cinder_backends:
            limit_container_types: cinder_volume
            ceph:                                <----------------- I changed this from 'rbd' to 'ceph'
              volume_group: cinder-volumes
              volume_driver: cinder.volume.drivers.rbd.RBDDriver
              volume_backend_name: ceph         <------------------ I changed this from 'rbd' to 'ceph'
              rbd_pool: cinder-volumes
              rbd_ceph_conf: /etc/ceph/ceph.conf
              rbd_user: cinder