Fiber Channel WANders Across Long Distances

FibreChannel implementations are constrained by distance: With repeaters andextenders the technology can go only 120 km, too short for cross-country datareplications. Two vendors recently introduced switches for linking FibreChannel SANs through optical connections, extending the current limitations.

EntradaNetworks’ Silverline router connects Fibre Channel to WANs such as T1/T3 andATM. In addition, Silverline supports Gigabit Ethernet and Fibre Channelconnections. The company also plans to support the iSCSI SCSI-over-IP standardwhen implementations hit the market.

Entradauses a modular architecture for its routers, enabling switches to be customizedfor a customer’s connectivity needs. Mike Harris, vice president of marketingat Entrada, says the company has road mapped nearly every major connectivitystandard for future Silverline iterations.

Harrisbelieves users will deploy Silverline in one of two ways. First, users whocontract with storage service providers (SSPs) may use the router forconnecting Fibre Channel host bus adapters (HBAs) in servers to SSP facilitiesover broadband connections like a T1 or OC-3. This will enable block-to-blocktransmission of data to the SSP. Second, enterprises with SANs located acrossthe country can use the router for replication between storage facilities,working around Fibre Channel’s 120 km limit.

Silverlinemoves Fibre Channel data across the WAN using an encapsulation technology.“We’re approaching it from a packet level,” Harris says. The router breaks thefile blocks sent over a Fibre Channel connection into packets, adding routinginformation for the receiving end. A second router on the other end decodes thepackets back into Fibre Channel data.

Harris saysthe company plans to add encryption services for businesses who need heightenedsecurity to meet federal regulations. Entrada also is considering the additionof dense wavelength division multiplexing (DWDM) technology for usersinterested in dedicating fiber for storage.

CrossroadsSystems, a stalwart of SCSI-to-Fibre Channel products, also introduced a FibreChannel-to-WAN router, ConXsan. Crossroads focused entirely on the ATM marketwith its release, but says that it makes product decisions based on customerfeedback.

“No matterwhat the infrastructure is, we’ll support it,” says Jeremy Ramsey, productmarketing manager at Crossroads. Ramsey points to a customer who ran ATM linesthroughout its campus as an example of a unique infrastructure supported byConXsan. The router was used to bridge between the SAN and the overallinfrastructure so server rooms and administrators could easily connect to theFibre Channel SAN.

Crossroadsdemonstrated the router at November’s Comdex in a joint presentation withCompaq. Using ConXsan and Compaq’s Data Replication Manager, the companiesshowed how the technology could be used to replicate SANs across broadgeographic distances.

“Eventuallypeople will want a single multiprotocol router platform that can do differentprotocols,” Ramsey says. He believes his customers want as much simplicity aspossible when dealing with multiple transport protocols.

BothEntrada and Crossroads are focusing on the midrange of the SAN market, bringingadvanced network technologies to smaller implementations. Other companies suchComputer Network Technology (CNT) have developed Fibre Channel-to-WAN routersat a higher end, out of the range of many SAN administrators.

WilliamHurley, analyst at The Yankee Group, says these midrange routers are mostappropriate for in-house applications, and that their use for long-distanceconnectivity is questionable. “It’s not there as far as robustness,” heexplains.

Hurleysays, however, that administrators should not have a hard time finding uses forthese routers. “They can sit at the edge of a SAN island, using IP to connectto the network,” he says. “It opens the door for all kinds of applications.”

EricSheppard, research analyst at IDC, says one significant application for FibreChannel-to-WAN routers is replication between data centers. He says the abilityto send storage data between remote sites improves data protection and givesadministrators the ability to directly replicate data for geographically basedInternet serving.

Althoughsome might argue that NT administrators are, in part, reluctant to deploy FibreChannel SANs because it adds an additional transport protocol to the network,Hurley says that is a false assumption. “This type of tool is consistent withthe type of openness that NT administrators are accustomed to,” he says.


EntradaNetworks, San Diego,

CrossroadsSystems Inc., Austin,Tex.,

ComputerNetwork Technology Corp.,Minneapolis

TheYankee Group, Boston,

IDC, Framingham, Mass.,

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