Symmetrix and the death of monolithic arrays

Burke says RapidIO was selected for its " non-blocking, low latency, high bandwidth, parallelism and cost efficiency – RapidIO has been used in a broad range of embedded applications from MRI systems to military fighter jets." He adds: "the Virtual Matrix Architecture doesn’t limit the fabric to being 2 RapidIOs; it could be 4 or 8 RapidIO networks running in parallel, or it could be built on a different infrastructure altogether – InfiniBand, FCoE/DCE (Data Centre Ethernet) – or whatever comes along in the coming years."

Geographic V-Max clusters

This 8-controller plus ASIC idea with back-end storage aggregated into a single virtual pool is reminiscent of 3PAR's T-class Inserv array. It even resembles a CX-4 Clariion controller with a virtual matrix backend according to one storage commentator. That would also play to the notion that V-Max is monolithic Symmetrix storage re-invented in a modular storage style.

Of course it should go way beyond that. We understand that the V-Max architecture can cope with 256 engines - 256 modular array components - and that these can be, or rather will be able to be, linked across geographical distances. That means that the global memory can be kept coherent across geographic distances and so can the single virtual storage pool.

It means in turn that data, such as virtual machine (VM) files and VM app data can be moved, or will be moved, automatically by the FAST software from one part of this geographically tightly-coupled storage cluster to another. This will work for both VMware and for Hyper-V. The idea of virtually instantaneous disaster recovery and optimising workload performance across hundreds of storage processors, across geographic distances, is very attractive.

Another aspect is that, from a virtualised data centre point of view, V-Max looks like storage that can be managed by and for virtualised servers, along with virtualised networks. The three virtualised elements of a virtual data centre - servers, storage and networking - will be able to work together for and be managed together by virtual data centre software. (There is a VMware announcement coming on April 21st, which will probably expand on this.)

Interconnect challenges

A question is whether the RapidIO switches that are currently available can cope with 256 V-Max engines. These switches collectively form a fabric with a backplane that provides the very high bandwidth and low latency interconnect glue enabling the separate V-Max engines to function as one. Increasing the number of engines sending messages across that backplane by a factor of 32 would greatly increase the packet load. Can RapidIO cope?

InfiniBand is looking set to have virtual segments created and it may be that RapidIO may go in the same direction. Alternatively, a different protocol might be used in future, with RapidIO bridges, as Burke alludes to above. It's understood that V-Max can have a different interconnect protocol applied if, say, the InfiniBand or 10gigE suppliers come up with a better one. The details of the interconnect are not visible to the software running in the V-Max engine processors so slotting in a new interconnect should not affect the upper layers of the V-Max architecture.

With EMC seeing that physical backplane designs simply cannot scale enough to support the potentially thousands of VMs running in a virtual data centre, it seems intuitively obvious that HDS and IBM will come to the same conclusion.

Their USP-V and DS8000 architectures will have to evolve to modularity too. Interestingly, NetApp is radically enhancing its storage array clustering capability with ONTAP 8.0 expected in a month or two, and has already said additional high-end hardware systems are on its roadmap.

We might see the top four storage array suppliers - EMC, HDS, IBM and NetApp (HP and Sun OEM HDS USP-V arrays) - all transitioning to scale-up/scale-out modular architectures at the high end of their product lines. ®