Is Fibre Channel over Ethernet the only way to a converged data center?

Some industry observers believe Cisco's enterprise clout will be enough to foster widespread acceptance of Fibre Channel over Ethernet, but others argue that such competing technologies as iSCSI and InfiniBand could work just as well for converging storage and data traffic.(Read a primer on FCoE technology.)

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"I remain unconvinced that FCoE is the answer," says Greg Ferro, an independent network architect and a vocal opponent of the technology. "If FCoE is the answer, what was the question?"

Once the IEEE completes its work of making Ethernet a low-latency, lossless transport option - and therefore reliable enough for storage traffic - iSCSI will be a suitable alternative to FCoE, Ferro says. The IEEE should wrap up work on those enhancements - which Cisco calls Data Center Ethernet and most other vendors refer to as Converged Enhanced Ethernet - this year. "As soon as you have a lossless connectivity fabric, then iSCSI works well for converging traffic. FCoE theoretically is faster, but iSCSI is much cheaper," he says. (Listen to a podcast on five things to love about iSCSI.)

Companies could use iSCSI for less mission-critical applications and turn to InfiniBand, a high-speed switching fabric used in high-performance computing applications, for more crucial applications, Ferro argues. 

For iSCSI to be as powerful an alternative as FCoE, however, vendors would have to develop some kind of network adapter to offload iSCSI from the CPU, as way network adapters are used today to offload TCP, contends Ian Rousom, corporate data-center network architect at defense contractor Lockheed Martin in Bethesda, Md. "Developing such a device would be similar to developing a converged network adapter," he says. "If that were to happen, iSCSI might be a better choice than FCoE."

For now, iSCSI potentially could be much slower than FCoE because of the additional layers of overhead involved, adds Rousom, who is considering FCoE and has looked into iSCSI as well. (Get test results of 12 iSCSI SAN servers.)

Arun Taneja, founder and consulting analyst at the Taneja Group, believes enterprises will adopt FCoE as a bridge technology but says iSCSI could work well for applications that aren't latency sensitive. E-mail applications that aren't deemed mission-critical, for example, might work well over iSCSI, he says.

"ISCSI is not yet proven at the 10-Gigabit enhanced Ethernet level," Taneja says. "Enterprises will start to play with it in 2009, and it is my guess that even after evaluating it and beating it up for months and months, they'll still drive it toward midrange applications and migrate to FCoE for critical applications."

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