Storage Must Wait for Cisco's Data Center Vision

Cisco's Nexus switch, the core of its data center and networking fabric strategy announced today, won't support many storage customers for months to come.

Nexus, the fastest and densest Ethernet switch on the planet, will initially feature 1- and 10-Gbit/s Ethernet connectivity with support for TCP/IP-related protocols. Featuring a new operating system, Nexus will converge various traffic types into a single "virtualized control plane," with a range of traffic management, quality of service, and security capabilities.

Performance claims are impressive: An initial Nexus 7000 platform includes a 10-slot chassis capable of supporting 256 10-Gbit/s Ethernet ports or 384 1-Gbit/s ports. Within six months, Cisco will add an 18-slot chassis capable of 512 10-Gbit/s ports or 768 1-Gbit/s ports. Throughput rates will reach 15 Tbit/s, Cisco says.

To tap that blazing speed for SANs, though, will take some time. Though Nexus is clearly Cisco's switch for unifying storage and networking in enterprise data centers, it won't ever support Fibre Channel directly, including 8-Gbit/s Fibre Channel (a key feature of Brocade's recently announced DCX Backbone switch). Instead, Nexus is meant to unify, not replace, the layer of Ethernet and SAN switches Cisco already offers.

But customers will be on hold for 8-Gbit/s Fibre Channel support on Cisco MDS SAN switches as well. MDS linecards supporting 8-Gbit/s Fibre Channel, and certified HBAs to support them, won't be ready until the second half of 2008.Another key storage element for Nexus is Fibre Channel over Ethernet (FCoE), which Cisco and other vendors are strenuously pushing to standardize with the T11 committee of the InterNational Committee for Information Technology Standards (INCITS). FCoE is not a standard yet and may not be for months to come. And Cisco is relying on specs for lossless "data center Ethernet," which are presently being developed in the Institute of Electrical and Electronics Engineers Inc. (IEEE) .

Cisco's also not including InfiniBand in the storage connectivity for Nexus. "We will not be incorporating InfiniBand into the Nexus platform," states Cisco spokeswoman Lee Davis. "InfiniBand is mainly needed for high performance computing (HPC) environments We do believe that some HPC applications may begin to use Ethernet with the new lower latencies, but most will stay on InfiniBand."

Without these key elements, the promise of Nexus as a data center unifier won't materialize for customers for awhile. But many high-end Cisco users aren't likely to let this hold them back from phased adoption of Nexus. For them, Nexus is the logical next step, even if it takes a few months, or even a couple of years, to get there.

Nick Lippis, analyst with Lippis Enterprises, says Cisco has "upped the performance to levels unseen. It's a new platform that will be with the industry for the better part of a decade." He thinks the importance of Nexus isn't diminished by the absence of some key elements, because Nexus is already ahead of high-end Ethernet switch competitors Force10 and Foundry in terms of performance; even other large vendors like EMC will have trouble matching this particular feature set.

"Cisco made a huge commitment here. They spent over a billion dollars over four years. No other company really has the resources and the intellectual property in the networking and storage spaces to match that," Lippis insists. "Cisco is unifying back-end, front-end, and backup switching in the data center."One thing: NAS customers will be able to tap the benefits of the Nexus environment right away. A new Cisco Catalyst 6500 switch, meant to connect to the Nexus, will support 10-Gbit/s hosts and NAS filers on first release. Each chassis will come with up to 130 ports of 10-Gbit/s.

Another newly announced product, the Cisco Catalyst 4900M Rack Switch, also supports 10-Gbit/s and 1-Gbit/s Ethernet for host and NAS connectivity. Each rack unit contains up to 24 ports of 10-Gbit/s, or up to 40 ports of 10/100-Mbit/s or 1-Gbit/s Ethernet with eight 10-Gbit/s uplinks.

So storage networking isn't missing from this announcement. But the full-fledged promise of SAN support will take awhile to materialize.

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