Fibre Channel

Fibre Channel is a serial computer bus intended for connecting high speed storage devices to computers. It started for use primarily in the supercomputer field, but has become the standard connection type for storage area networking. Despite its name, Fibre Channel signalling can run on both twisted-pair wire and fibre optic cables.

Fibre Channel started in 1988 as a way to simplify the HIPPI system currently in use for similar roles. HIPPI used a massive 50-pair cable and gigantic connectors, and had limited cable lengths. Fibre Channel was primarily interested in simplifying the connections and increasing the lengths, as opposed to increasing speeds. Later it broadened its focus to address SCSI disk storage, providing higher speeds and far greater numbers of connected devices.

It also added support for any number of "upper layer" protocols, including SCSI, ATM and IP, with SCSI being the predominant usage.

There are two major versions of the Fibre Channel protocols:

• Version 1 is known as "arbitrated loop". In this design, all devices are in a loop or ring, similar to token ring networking. Adding or removing a device from the loop causes all activity on the loop to be interrupted. The failure of one device causes a break in the ring.

• Version 2 is known as "switched fabric". All devices are connected to switch devices, similar conceptually to Ethernet switches or routers. The switches manage the state of the fabric, providing optimized interconnections and also security. Many version 2 products are designed for backwards compatibility with version 1 devices.