How to set RBD backend for Nova ephemeral storage

We give here the instructions to set RBD (Ceph) as the ephemeral storage backend.

We assume the OpenStack cluster is connected to a Ceph cluster via ceph-proxy charm.

To enable RBD set the following parameters on nova-compute charm:

juju config nova-compute libvirt-image-backend=rbd
juju config nova-compute rbd-pool=cinder-ceph

Add the following relations to nova-compute:

juju add-relation nova-compute ceph-proxy
juju add-relation nova-compute cinder-ceph

Log in to one nova-compute units. You should find the following configuration in /etc/nova/nova.conf:

[libvirt]

images_type = rbd
images_rbd_pool = cinder-ceph
images_rbd_ceph_conf = /var/lib/charm/nova-compute/ceph.conf
inject_password = false
inject_key = false
inject_partition = -2
rbd_user = nova-compute
rbd_secret_uuid = 514c9fca-8cbe-11e2-9c52-3bc8c7819472

Your OpenStack cluster is now ready to spawn instances with ephemeral disk on Ceph!