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This feature allows the gateway to take advantage of the virtual N_Port ID Virtualization switch standard and re-present each blade server N_Port login as multiple virtual N_Port logins to the FC director. Once the virtual blade server N_Port is logged into the FC director, the FC director can treat it as a server logged into the SAN, including zoning it to specific ports and assigning qualities of service to traffic coming from that blade server.
But there are differences with how the two vendors implement their gateways, including which vendors' blade servers are supported. Brocade's blade server SAN switch supports blade server chassis from more vendors, including Dell, Fujitsu, HP, Hitachi, IBM, Intel and NEC. Cisco's Fibre Channel Blade Switch currently works only in HP and IBM blade server chassis.
The gateways also scale back on certain software features their switch OSes typically support. For instance, Cisco doesn't support IVZ on its Fibre Channel Blade Switch, while Brocade disables nearly all features its FC switches support such as ISL trunking, FC-AL and Brocade Fabric Manager. Disabling switch features such as ISL trunking happens because the switch presents itself to the FC director as an N_Port instead of an E_Port or EX_Port, so the FC director recognizes the gateway as a storage device and not an FC switch.
Changing this requires the introduction of a feature called F_Port trunking into F...
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C SANs. F_Port trunking is similar to interswitch link trunks between switches except that it's designed to create trunks between storage devices, such as server FC host bus adapters and gateways, and the target device. Driven by technologies like blade servers and server virtualization, it allows FC traffic to go down different paths but still assure in-order delivery regardless of which path the traffic takes. However, "F_Port trunking does not exist in the [Brocade] 48000 today," says Mario Blandini, Brocade's director of product marketing.
Because Cisco has incorporated services like VSANs and IVZ into its SAN-OS, it leads Brocade in many respects. Brocade's resources remain split between developing the next-generation 48000 and supporting legacy McData products. Though Brocade's planned 2008 release of a new FC director may tilt the balance, it will depend on what new features are built into its new director. In the meantime, firms shouldn't deploy more than one or two fabric services at one time (due to cost and complexity) until more of these services move off switches and director blades and into the core OS of the FC director products.
For a detailed chart listing Brocade and Cisco Fibre Channel director features, go to http://searchstorage.techtarget.com/magazineFeature/FCdirectorschart.
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