EMC Reworks Symmetrix

While I was expecting EMC to announce a new generation of Symmetrix earlier this week, I must admit I was surprised that it wasn't just the usual bigger, stronger, faster, but a whole new Symmetrix architecture, and it was, GASP!, modular! Where Syms of old were hulking refrigerators -- OK, more like the Sub-Zero in the Food Network test kitchens -- the V-Max is a cluster of dual Xeon-powered "engines" that even in the initial configuration of up to eight engines can deliver more ports, I/O, and capacity than a DMX-4.

The key is the high bandwidth, non-blocking, low-latency, RapidIO-based "Virtual Matrix Interconnect" that enables EMC's RDMA-on-steroids model that allows the processors in any "engine" to directly access memory in any other engine in the cluster -- even if EMC doesn't use the word "cluster." With this architecture EMC doesn't have to try to maintain cache consistency across multiple cluster members; all their memory is one common pool. Disk enclosures are multi-pathed to multiple engines, so any data is accessible via a port on any engine, either directly or over the interconnect. While EMC is only supporting up to 8 engines in a cluster today, the architecture allows up to 256.

As far as RapidIO goes, it was new to me, too. If someone described the application, I would have guessed InfiniBand was the interconnect of choice, but EMC's engineers probably know something I don't. The current design gives each engine 80 Gbit/s of bandwidth to the interconnect, and EMC says they can easily upgrade to faster RapidIO or substitute InfiniBand or Ethernet when the time comes. More info on RapidIO is available at http://www.RapidIO.org.

This modular architecture brings to Syms one of my favorite features of Equallogic's and HP/Lefthand's iSCSI arrays, where adding capacity can also add additional I/O bandwidth and cache to an array group that's managed as a single entity and has a common pool of free disk space. Each V-Max engine has 16 back-end 4 Gbit/s ports for disk enclosure connections and 16 mix-and-match FC (still 4 Gbit/s), Ficon, and/or Gigabit Ethernet (for replication and iSCSI connectivity) user front-end ports.

It also will allow EMC to "federate" multiple clusters for rapid replication and mirroring, common management, and other stuff they either haven't figured out yet or aren't telling this intrepid reporter. In no small part, I think they're waiting for some customers to digest the new architecture and come up with applications for federation.But V-Max is still a Symmetrix, and Sym buyers aren't known as big risk takers. As a result, V-max doesn't use all the latest technology; it is based on the previous-generation Xeon 5400 and not the Nehalem Xeon 5500s that came out last week. Given the performance, and especially I/O performance boost Intel managed to squeeze out of Nehalem, EMC has a clear roadmap to its next model. I was also surprised by the lack of 10-Gbit/s Ethernet support, especially given EMC Chairman Joe Tucci's shout-out to Cisco's Unified Computing System two minutes into the introduction of the virtual press conference.

I would think that the customers coming up with the coin necessary to be buying Syms are also buying Ethernet switches with 10-Gbit/s uplinks and would therefore prefer to use a few 10-Gbit/s ports for iSCSI than a whole bunch of the 1-Gbit/s ports on the V-Max. It also means those Cisco UCS uses will need to bridge FCoE to Fibre Channel to connect to a V-Max.

And that's just the hardware side of things. Software and management are a whole 'nother blog entry. More next time.

Howard Marks is chief scientist at Networks Are Our Lives Inc., a Hoboken, N.J.-based consultancy where he's been beating storage network systems into submission and writing about it in computer magazines since 1987. He currently writes for InformationWeek, which is published by the same company as Byte and Switch.

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