For data centers, the advantages of Fibre Channel over Ethernet are compelling: lower capital costs, less cabling, less cooling, reduced energy consumption and fewer adapters.
Given the newness of the technology, most early adopters are still in the test phase. But that is expected to change over the next few years as virtualization and blade server technologies pack ever more servers into racks.
FCoE is a protocol for seamlessly transporting Fibre Channel frames over 10 Gigabit Ethernet. It essentially extends Fibre Channel into the Ethernet environment, providing an evolutionary approach to I/O consolidation. In addition to encapsulating Fibre Channel frames in Ethernet packets, FCoE extends the Ethernet protocol so packets are not lost when the network becomes congested. It also maps between Fibre Channel IDs and Ethernet MAC addresses.
A committee of the INCITS T11 organization ratified the FCoE protocol as a standard last summer. Technologies that rely on the protocol, such as converged network adapters, are just starting to appear from manufacturers such as Brocade, Emulex and QLogic, among others.
The Lure of FCoE
“If we’re going to move to the world of the virtual data center and cloud computing, we need to bring our network and data stacks together,” says Zeus Kerravala, distinguished research fellow at Yankee Group. “Fibre Channel over Ethernet helps us do that.”
One needed change is to modify the Ethernet protocol to make it lossless. Normally, Ethernet allows frames to be lost and then retransmitted. This works fairly well for LANs because it’s cheaper and less demanding of the network. But on storage networks, dropped packets are unacceptable because the loss-and-retransmit paradigm slows down file transfer.
“In a storage environment, dropping frames isn’t tolerated,” says Bill Dunmire, director of product management at Brocade. “You need transport that is lossless. That is what Fibre Channel provides.”
Just Taking Hold
FCoE is still in the initial stages of adoption. “We’re early in the technology. The industry is really in a test phase,” says Dunmire. “Customers are testing the technology with industry and following its evolution.”
But the transition to prototype installations is starting, and pilots are expected in federal agencies this year. “We see it going into budgets in 2011,” says Shaun Walsh, vice president of corporate marketing at Emulex.
Before there can be widespread deployment, some performance considerations must be addressed. FCoE introduces additional overhead into the network and slows down transmission. The current generation of FCoE is fast enough for basic storage networks, but isn’t sufficient for heavy-duty applications yet.
As a result, Dunmire predicts that agencies will initially adopt FCoE for Level 3 applications and gradually move up into Level 2. “High-volume databases will stay on Fibre Channel,” Walsh says.
The current rate of adoption is relatively slow because organizations aren’t going to abandon installed Fibre Channel in one fell swoop, Kerravala says. But it’s important for IT organizations to start thinking about FCoE and plan for its adoption.
“People have to understand that we can’t judge this technology on current adoption — it’s going to be a long-term trend,” he says. “People should start their education process today. When FCoE adoption does happen, it’s going to happen pretty quickly.”
How FCoE Works
FCoE encapsulates Fibre Channel packets in Ethernet frames and sends them over Ethernet LANs to rack-top switches. The switches then separate Fibre Channel storage area network traffic from Ethernet LAN traffic and push them on their respective ways.
Instead of having separate Fibre Channel host bus adapters and Ethernet network interface cards in each server, these are combined in a single converged network adapter and fed over a single cable. This cuts the number of adapters and cables in half and reduces clutter, consumption and cost.
One caveat: For redundancy, organizations still need multiple connections, but FCoE cuts that number in half as well.
SOURCE: Fibre Channel Industry Association