the spec sheet for the HUS seems to indicate that for the first two tiers they are using the BlueArc Mercury 50/55 and on the higher tier the Mercury 100/110.
The throughput of the Mercury seems to lack behind the throughput of the HUS itself. - around 1.4GB/sec peak for a 2-node 50/55 and 4.5GB/sec for a 4-node 100/110 vs between 6GB and 12GB/sec for the HUS back end. Though I suppose if it was an issue HDS might happily switch out the Mercury platform for a Titan platform. Though maybe they are reserving the Titan for their VSP version of the HUS and force customers to go VSP if they want HUS with Titan..
Still don't see any evidence the BlueArc platform supports any sort of thin provisioning, so sharing storage between file vs block you'll probably have to be more careful vs something that could reclaim storage between the different types of access. Too bad the low end doesn't support wide striping? What an odd decision.
Seems to be a really nice upgrade vs the AMS 2k which was a pretty bland system. Given HDS has to have a completely separate "module" for the file access (as opposed to running another software module on the same CPUs like Netapp - and maybe EMC ? does) - I wonder how that will impact the pricing vs the competition.