No gigs for 4-gig fibre

A working 4Gbit/s Fibre Channel network is being demonstrated at the Cebit show this week in Germany.

Emulex, Seagate Technology and Xyratex Technology have collaborated to produce the first full-function 4Gbit/s demo, with Xyratex's storage enclosure technology, Seagate's 4Gbit/s enterprise HDDs and Emulex' InSpeed SOC 422 Fibre Channel embedded storage switch.

Most Fibre Channel SANs currently operate at 2Gbit/s. A forthcoming 10Gbit/s Fibre Channel network will offer five times faster links but will not be backwards-compatible with today's 2Gbit/s switches, HBAs and drive array controllers. As such, an interim 4Gbit/s standard has been developed to add a little more speed and work with existing 2Gbit/s gear.

However, customers have not, until now, been shown a working 4Gbit/s Fibre Channel network. The demonstration shows that end-to-end 4Gbit/s networks require HBAs, switches, drive arrays and drives all to be 4Gbit/s-capable.

QLogic Corp. has also been in the forefront of efforts to have 4Gbit/s fibre channel adopted. But the company is hedging its bets and promoting 10gig as well.

With companies such as Brocade Communications Systems suggesting multi-level SANs are a development for the future, then SAN backbone links will need to aggregate multiple edge links. A 4Gbit/s backbone would only be able to aggregate two existing 2Gbit/s links. A 10Gbit/s link would be more effective. There is also little evidence as yet that customers are suffering from the SAN slowdown which would encourage the use of faster Fibre Channel.

However, 4Gbit/s Fibre Channel hardware products are pin-compatible with 2Gbit/s products and the chips involved will be little different in cost -- meaning it will be easy to upgrade. The alternate Ethernet-based iSCSI SAN technology will move directly from 1Gbit/s Ethernet to 10Gbit/s and that could force the issue.

Or it might be the case that 4Gbit/s Fibre Channel offers too little. By the time SAN speed needs have become more apparent, 10Gbit/s products will be available and ready to take up the slack.

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