Hi, This is something that’s not exactly clear in the documentation and so I thought I’d ask here. There are currently two ways to set disk IO limits, or QoS: through Cinder QoS values or through Nova flavours. My question is, what’s the difference exactly? I assume that Cinder QoS only applies on Cinder volume, but is the same true for flavour QoS? In other words, is QoS through flavour supposed to apply to both Cinder volumes and ephemeral storage or is it only for ephemeral storage? Additionally, I'm under the assumption that once you provision a block device of a certain type with QoS associated to it, it becomes impossible to modify the values afterwards. Is that correct? This is a strange behaviour, considering that technically, you should be able to change QoS when it’s set through flavour using a simple resize. Please correct me if I’m wrong. I feel that this could be better explained in the current documentation. Jean-Philippe Méthot Openstack system administrator Administrateur système Openstack PlanetHoster inc.