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Until quite recently, Fibre Channel and Ethernet networks were mutually exclusive. Sure, you could encapsulate Fibre Channel within TCP/IP to run over long distance IP networks - that's how the iFCP and FCIP bridging schemes work - or you could bridge the two, but when it came to networked storage, each server used either Fibre Channel or an IP SAN connection.

Now that's changing: as Techworld reported earlier this week, a consortium of networking suppliers put together a specification to run the Fibre Channel protocols over Ethernet, with no need for encapsulation, or indeed for an IP layer at all.

FCoE's proponents - who include Brocade, Cisco, EMC, Emulex, IBM, Intel, QLogic, Sun and others - argue that it will provide a seamless way to extend a Fibre Channel SAN to more servers, without having to fit them all with Fibre Channel HBAs, install Fibre Channel switches and cabling, and so on. It will do this by making Ethernet loss-less, thanks to new specs around congestion management.

Of course, you can build an IP SAN today using iSCSI, but that requires each server to do some heavy-duty number crunching, especially at 10Gbit/s speeds. So you either want an expensive TCP offload engine (TOE) - basically, a super-intelligent NIC - or you'd better have quite a few processor cycles going spare if you want to do it in software.

And as Emulex senior marketing director Joe Gervais says, iSCSI is "a different management paradigm- it encapsulates SCSI packets differently from Fibre Channel." He claims that by comparison, the only difference between FCoE and Fibre Channel will be the wires - management will be the same.

He adds that, just as in the early days of LANs we used to run multiple protocols on the same wire - TCP/IP, NetWare, DECnet, etc - this allows Fibre Channel and TCP/IP to share a connection.

So is FCoE the Holy Grail of storage networking - the long-awaited technology that will finally enable the 30 to 50 percent of corporate servers that aren't currently connected to the SAN to join in? Up to a point, Lord Copper...

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