Storage Managers Ponder New Interconnects

A quick scan of recent headlines shows a growing list of networking schemes aimed at linking equipment in enterprise data centers. But storage managers may be able to sit out the current kerfuffles over InfiniBand versus 10-Gbit/s Ethernet, RDMA, iWARP, OpenFabrics Enterprise Distribution, and the like.

This week's Supercomputing 07 (SC07) conference in Reno, Nevada, was a showcase for storage vendors pursuing the high-performance computing (HPC) market. Most announcements and demos centered on InfiniBand as a mainstay interconnect, with multiprotocol "gateways" from Cisco, Voltaire, and Qlogic in the mix.

At least one analyst, however, thinks storage pros can use a fine-gauged filter right now.

"We don't see InfiniBand as the primary storage interconnect now or in the future," says analyst Bob Wheeler of the Linley Group consultancy. While InfiniBand will continue to reign as the network for localized server clusters, in his view Fibre Channel over Ethernet (FCoE) is the protocol for storage professionals to watch.

"There have been some significant recent announcements from Cisco/Nuova, Emulex, QLogic, and Intel on the Ethernet NIC side of FCoE," Wheeler says. In the future, while high-end storage arrays will continue to support Fibre Channel even as faster Ethernet spreads, he envisions FCoE NICs eliminating the need for servers to sport dueling Fibre Channel HBAs and 10-Gbit/s Ethernet NICs.Nascent FCOE has garnered interest from high-profile users, but products aren't mainstream yet.

Wheeler also thinks there are storage possibilities in protocols that use remote direct memory access (RDMA), a technique deployed in InfiniBand for bypassing a computer's operating system in passing data from one server to another. Since it's worked well in InfiniBand, RDMA has been adapted for 10-Gbit/s Ethernet as iWARP -- Internet Wide Area RDMA Protocol -- by a small but vocal group of implementers that includes Chelsio, NetEffect, and NetXen. At present, however, iWARP remains a novelty.

A few players are also focused on combining iSCSI with RDMA in a protocol called iSER (iSCSI Extension for RDMA), an approach favored by Voltaire that looks to be part of specs in development at the OpenFabrics Alliance, to which Chelsio, Cisco, HP, IBM, NetApp, NetEffect, NetXen, QLogic, and Sun also belong, among many other suppliers.

The OpenFabrics project is working on an OpenFabrics Enterprise Distribution and other mechanisms for unifying InfiniBand and Ethernet, but Wheeler says the group still needs to achieve commonality in features that support both networks.

Bottom line? Wait and see, says another analyst, who thinks storage suppliers will try to muddy the waters to their own advantage. "There will be an on-going battle for the next few years at least," writes Gartner analyst Joe Skorupa in an email today. "IB will be used for compute clusters and some clusters will use IB or IB-FC gateways for storage access. Some lower-performance clusters will use 10GE and will use 10GE/iSCSI or FC for block storage access. Some will use 10GE NAS (NFS or CIFS) for requests with responses delivered over FC as blocks."In his view, vendors will "try to stir an already bubbling cauldron of confusion over what to do." Some may even avoid standards and attempt to lock customers into their own designs. "Not a good thing," Skorupa avers.

Whether or not proprietary schemes are good would be debated by vendors like Brocade, which recently unveiled its own fabric design.

But a third analyst, who asked not to be named, thinks storage managers can make their lives a lot simpler by scoping out some basic economics. "Storage managers pay attention to operational ease of use, not protocols," this analyst states. "If changing from what they have to something else entails risk, headaches, or hassles, they will be reluctant to implement. If it doesn't, they're interested. Most of the stuff you are talking about is aimed at taking the risk, headaches, and hassles out of using 10G Ethernet with storage. Then again, iSCSI already does that. It's just too inexpensive for the server and storage vendors to make enough money."

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