For many years, the prevailing wisdom behind storage networking was that you had a choice between Ethernet and Fibre Channel. Then, along came the converged networking adapter (CNA) and Fibre Channel over Ethernet (FCoE) and suddenly there was an economically viable way to have both, albeit a Fibre Channel layer running on an Ethernet fabric.

But now it seems that the All-Things-Under-The Ethernet movement was premature at best -- that a more likely scenario is that enterprises, even those that don't already have Fibre Channel, will still find value in building concurrent Ethernet and Fibre Channel networks.

Why would anyone want to do this? Why stick with an 8 Gbps FC infrastructure when Ethernet is on the way to 40 Gb and even 100 GB?

Well, as the Register's Chris Mellor spells out pretty clearly, the simple fact is that even with FCoE, Fibre Channel traffic will not simply transition over the Ethernet. In particular, the SAN management functions that FC users have come to rely on will not be available on the leading Ethernet switches. Sure, an FCoE switch will still be routed to its proper destination, but none of the higher management functions will be available unless you are in a full Fibre Channel environment. Rather than seeing it as Fibre Channel over Ethernet, he argues, we should consider Fibre Channel and Ethernet.

Mellor was highlighting the strategy behind QLogic's decision to launch an Ethernet adapter line, a move that allows the company to cover all the bases in enterprise networking: Ethernet, FC, FCoE and InfiniBand. Rather than simply bridge the disparate networks using FCoE, QLogic recognizes that even a CNA has to cope with end-point devices that will still be one protocol or the other. That's why it is devoting time and money to come up with Ethernet-only devices like the 3100 Series adapter -- built on technology it acquired from NetXen -- rather than loading everything into the CNA and calling it convergence.

This dual-networking approach is evidenced by some of the latest storage systems -- none of which offer unified Ethernet/FC capability in a single box, not even a virtualized one. Infortrend is the latest to get into the game with its Enterprise Scalable Virtualised Architecture (ESVA), which is currently available in three Fibre Channel flavors -- the F20, F40 and F60. A pair of iSCSI models -- the E20 and E60 -- are due out later this year.

In one sense, this is kind of a no-brainer. Convergence was never intended to stretch from end to end. It's merely a means to reduce duplication of wiring and other infrastructure in between. But it also puts aside the notion that Ethernet is going to take over the enterprise completely.

Some of you may have misunderstood my comment a few weeks ago that Ethernet has the greater cachet when it comes to forming the enterprise fabric. That's still true (at least compared to Fibre Channel -- InfiniBand is another story), but it by no means holds all the keys to advanced storage and data networking.

The beauty of network convergence is that it lets you extend various protocols to the environments that can best take advantage of their particular feature sets.