Policy based tiering
Policy based tiering is in there because HP offer different members of the X9000 family which have contrasting storage properties, e.g There's a gateway product (X9300) that can sit in front of an existing array, an all SAS version (X9320) and SAS midline (X9730). All can be part of the same cluster and namespace so data can be placed on the most appropriate tier based on access frequency or age etc. I'm told metadata processing is distributed across all nodes so there's no bottleneck on metatdata and so less need to accelerate this with flash. If your contact at HP UK doesn't know anything about this, then you're probably talking to the wrong person :-(.