Electronic Design

Fibre Channel Over Ethernet Adapters Simplify Infrastructure And Save Money

The 8000 series converged network adapters (CNAs) from QLogic Corporation aren’t just new network interface cards (NICs) or host bus adapters (HBAs). Instead, they’re the first CNAs to allow the Fibre Channel (FC) storage-area network (SAN) protocol to run directly on an Ethernet local-area network (LAN).

SANs have grown in importance over the years as organizations now have tons more data to store. Most of those original networks employed FC, which uses high-speed fiber connections to move data to and from redundant arrays of independent disks (RAIDs) and “just a bunch of disks” (JBODs) to servers. FC SANs have continuously increased their data speed from just over 1 Gbit/s in earlier systems to 8 and 10 Gbits/s in current systems.

While these legacy systems have essentially kept pace with IT needs and technology, another option emerged in parallel—iSCSI, an interface that allows common disk-drive protocols used in older parallel data connections (Small Computer Systems Interface) to be transmitted over standard Ethernet connections.

Many newer SANs have adopted this technology because it’s clearly cheaper than the heavy-hitting FC and makes storage systems compatible with all existing servers and other networking gear based on Ethernet. And, today’s 10-Gbit/s speeds are readily achievable with iSCSI interfaces.

Yet there is a huge market of entrenched FC users who want to merge their FC boxes into Ethernet local-area networks (LANs). The result of this need was the creation of new protocols like the Internet Engineering Task Force (IETF) Fibre Channel over Internet Protocol (FCIP) and Internet Fibre Channel Protocol (iFCP). FCIP tunnels data between SANs over IP networks using Ethernet, while iFCP permits the FC protocol to be run in an IP Ethernet LAN by replacing the FC switching and routing functions with IP components and techniques.

The latest in this series of efforts to put FC on Ethernet is the emergence of the Fibre Channel over Ethernet (FCoE) standard built by the T11 FC group within the International Committee for Information Technology Standards (INCIT). FCoE is the standard for transporting FC frames over Ethernet LANs.

While iSCSI encapsulates the SCSI codes and data into IP packets for transmission over Ethernet, FCoE maps the FC commands and data directly into Ethernet frames, eliminating the TCP/IP connection. That means FC can run right along with IP traffic on an Ethernet LAN. The FC-0 (physical layer) and FC-1 (encoding/decoding) layers are replaced with the standard Ethernet physical layers (PHYs) and media access controller (MAC) layers combined with the FC mapping function. Add to this the making of Ethernet into a lossless transport system by using the Ethernet PAUSE capability that manages congestion and contention on the network.

The beauty of this arrangement is that a single FCoE CNA can now replace the separate Ethernet NICs and FC HBAs needed in a server, saving space, power, and costs. The outcome is that data centers can increase functionality while reducing costs and complexity by using a single set of cables and switches.

The new QLogic CNAs are available in two varieties. The QLE8042-CK PCI-E to FCoE dual-port CNA ships without transceivers installed, though it targets use with low-cost SFP+ transceivers. The QLE8042-SR-CK PCI-E to FCoE dual-port CNA ships with two optical transceivers installed. Both devices run at 10 Gbits/s full duplex on fiber or copper interfaces compatible with SFP+.

QLogic Corp.www.qlogic.com

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