roles:
-- [mon.a, mgr.x, osd.0, mon.b, mds.a, mds.b, client.1]
-- [mds.c, mds.d, mon.c, client.0, osd.1, osd.2]
+- [mon.a, mgr.x, osd.0, osd.1, osd.2, osd.3, mon.b, mds.a, mds.b, client.1]
+- [mds.c, mds.d, mon.c, client.0, osd.4, osd.5, osd.6, osd.7]
openstack:
- volumes: # attached to each instance
count: 2