When a Router's Not a Router

You know an emerging technology is hot when vendors new and old latch onto the same buzzword for a multitude of different products.

We're talking about storage routing here: Everyone either has it or needs it, but no one is quite sure how to define it. Confusion reigns on the exact meaning of the term "storage routing," and unlike obscenity, you might not know it when you see it. A simple Web search for storage routers, for instance, might turn up products as wide-ranging as multiprotocol switches, distance gateways, and virtualization appliances.

The brains behind product branding efforts aren't helping either. The forthcoming "Storage Router" from EMC Corp. (NYSE: EMC) which Hopkinton marketing insists is only a working title, subject to change – sticks out as a classic case in point. In fact, you wouldn't get EMC to disagree with that assessment.

"I don’t think discussing this product in the context of a router is appropriate," says Rob Sadowski, product marketing manager for the "Storage Router." "It has caused some confusion."

Instead of routing, EMC's device virtualizes storage-network traffic, inspecting packets and redirecting them to appropriate areas in conjunction with other vendors' switching platforms (see EMC Takes Storage Router for a Spin}.Perhaps EMC's apparent about-face has as much to do with diplomacy as technology: The company resells Brocade's Multiprotocol Router as the EMC Connectrix AP-7420B, one of the devices EMC's Storage Router will team up with. Two routers for the price of four, anyone?

But this isn't just a salesperson's worst nightmare; it could be a SAN buyer's, too. Parsing subtle differences among products that purport to "route" data among storage networks can lead to dizzying consequences. We take aim at this task in this month's Byte and Switch Insider, Storage Routing Unmasked, imposing order on this chaotic hodgepodge of options.

At the heart of the frenzy: improving connectivity between and among SANs. Like routers in IP-based networks, routing in the storage world proposes to interconnect self-contained SANs to create a smooth flow of data among them.

"We're always looking for better ways to move data around, that's the thing we do the most," says Dan Pollack, operations architect at America Online.

Pollack and other data-center folk have grappled with this problem for several years. They've built high-port-count SANs to consolidate resources, but that creates unwanted complexity and scaleability ceilings. They've tried to physically merge fabrics, but that leads to intolerable disruptions that ripple through both sides of the SAN when changes occur. And they've raced around trying to directly connect devices on different SANs, but that has stretched their human resources, not to mention sanity."With routing, we don't have to run cables all over to get ad hoc connectivity," says Pollack.

The routing that Pollack refers to involves devices that interconnect SANs – SAN routers, for lack of a better term – and enable administrators to create zones across them. While this facilitates logical segmentation, it also maintains physical separation between the networks for better manageability.

Products Brocade Communications Systems Inc. (Nasdaq: BRCD), Cisco Systems Inc. (Nasdaq: CSCO), LightSand Communications Corp., and McData Corp. (Nasdaq: MCDTA) perform these functions today.

But even within this niche, differences remain. That's because SANs don't exactly correlate to their IP predecessors. Instead of functioning as pure Layer 3 devices, SAN routers tweak Layer 2 operations with unique Layer 3 routing techniques. Brocade and McData call it Fibre Channel Network Address Translation (FC-NAT); Cisco has Virtual SANs (VSANs) and Inter-VSAN Routing (IVR); and LightSand employs Autonomous Region/Domain Address Translation (AR/DAT). Oh, and Cisco will add its own version of NAT with a software upgrade this month.

A standard is on the way, dubbed Fibre Channel Fabric Routing (FC-FR), and it's due for initial public review in October 2006. Many enterprises have pressing needs for this kind of routing and can't afford to wait, but even those who do shouldn't expect a panacea. The real interoperability concern is with SAN routers and the switches to which they connect. For that, vendors are on their own with backward-engineering of competing products.Storage routing is clearly a conundrum. But the need for better SAN interconnectivity guarantees it's a conundrum the industry is bent on solving.

— Brett Mendel, Senior Analyst, Byte and Switch Insider

Storage Routing Unmasked is available as part of an annual subscription (12 monthly issues) to Byte and Switch Insider, priced at $1,350. Individual reports are available for $900.

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