Apr 01 2010

CNAs: The Next Wave of Consolidation

Converged network adapters cut costs and smooth cabling snarls.

Just as virtualization has spurred consolidation of servers and storage, converged network adapters (CNAs) are now poised to bring about consolidation of storage I/O.

CNAs let IT administrators combine storage area networks and Ethernet LANs, eliminating half their network cards and the associated cabling to save energy and money and simplify network management. Brocade, Emulex and QLogic are among the first manufacturers to offer such products.

Working with Fibre Channel over Ethernet, CNAs combine the functionality of a Fibre Channel host bus adapter with an Ethernet network interface card on a single card with one or more Ethernet connectors.

“Converged network adapters have the potential for large cost savings because you have fewer adapters — one instead of two — and out of that adapter comes one cable instead of two, which goes to one converged switch,” says Seamus Crehan, vice president of the Dell’Oro Group market research firm.

The space savings can be important as well, notes Shaun Walsh, vice president at Emulex. “With the growth of blade servers and virtualization, as enterprises move to 10 Gigabit Ethernet midplanes and server virtualization drives I/O, you don’t have enough physical space to get the horsepower out of the server,” he says.

Making Connections

Fibre Channel cable connects to the SAN for storage through a Fibre Channel HBA, and an Ethernet HBA connects the server to the enterprise network. With the growing use of virtualization and blade servers, the result is a proliferation of cabling, HBAs and Ethernet cards that consume power, complicate management and decrease reliability.

“CNAs allow administrators to use less cabling and have lower port counts,” says Deni Connor, principal analyst at Storage Strategies Now. “A CNA enables Fibre Channel over Ethernet [FCoE] in which a Fibre Channel packet is encapsulated in an Ethernet packet.”

Because CNAs are an emerging technology and the first products just recently appeared on the market, there are few early adopters to date. CAN pricing varies, depending on model and features, but is typically is several hundred dollars more than most dual-port 10 Gigabit Ethernet cards.

Still, the undeniable attraction of CNAs is such that analysts like Connor and Crehan are predicting a fairly rapid adoption of FCoE technology as data center administrators become more familiar with it and more comfortable with the idea of combining their LANs and SANs. “We’re going to have a lot of people kicking the tires to see if they want to adopt it or not,” Connor says.

Tom Hammond-Doel, vice chairman of the Fibre Channel Industry Association, agrees. “What we’re seeing now is there are a few FCoE deployments out there, but those are early adopters trying to figure it out,” he says. “We’ll start to see adoption coming in early 2011.”

Connor sees FCoE CNAs as a supplement to SANs rather than a full-scale replacement in most installations. “In a converged network, administrators would replace HBAs and Ethernet adapters with FCoE,” she says. “They are saving energy, using fewer adapters in the server.”

Protocol for Change

Fibre Channel over Ethernet (FCoE), the native tongue of converged network adapters, is a protocol for seamlessly transporting Fibre Channel frames over 10 Gigabit Ethernet.

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, and 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 such as CNAs that rely on the protocol are just starting to appear.