Speed wars: Fibre Channel vs. Ethernet


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Storage networking performance today
Until the advent of 8Gb/sec FC and 10Gb/sec Ethernet over copper, your only option for fast storage networking was 2Gb/sec FC, until the middle of 2005 when 4Gb/sec FC became commercially available. On the IP/Ethernet side, 10Gb/sec over optical was available, but too costly (more than $4,000 per connection) to be practical except for unusual situations. Organizations that wanted IP-based storage networking opted for iSCSI over 1Gb/sec Ethernet links.

iSCSI vs. Fibre Channel

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The market sorted itself out on the basis of price and performance. Enterprise data centers opted for FC to get higher performance for their SANs and were willing to pay top dollar in terms of the cost of the components and skilled FC technicians. Small and midsized organizations went for the lower performance of 1Gb/sec Ethernet for iSCSI SANs in large part due to its lower cost and the ability to leverage existing IP networking skills.

FC holds the advantage in terms of performance, but iSCSI-IP commands a clear advantage from a cost standpoint. At 1Gb/sec, Ethernet requires only a simple NIC card ($50) in the server vs. an FC HBA ($800 to $1,200). The cost of Ethernet switch ports are a fraction of the cost of FC switch ports, and at 1Gb/sec, most servers don't even require a TCP/IP offload engine (TOE) to reduce the overhead of processing the IP stack.

Even without backup to disk or port consolidation projects in the works, interest in 4Gb/sec FC is building, says TheInfoPro. "It's mainly helpful for ISLs [inter-switch links], not for app performance. Still, companies say they'll take it even though they don't need the performance as long as they don't have to pay a premium," says Ken Male, founder and chief executive officer at TheInfoPro.

No worry there. Vendors don't expect to charge a premium for 4Gb/sec FC. "By the end of this year, everything will be 4Gb/sec FC at the same price as 2Gb/sec," says Greg Scherer, chief technology officer at Emulex Corp., an FC components provider in Costa Mesa, CA.

As with the shift from 1Gb/sec to 2Gb/sec FC, 4Gb/sec FC is backward-compatible, so it can ratchet down when it senses the slower link. When the move to 8Gb/sec FC occurs, the same should hold in terms of price and compatibility. Similarly, Ethernet has moved from 10Mb/sec to 100Mb/sec to 1Gb/sec without compatibility issues. The industry expects no compatibility problems moving to 10Gb/sec Ethernet over copper.

This was first published in February 2006

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