Fibre Channel

(storage, networking, communications)An ANSI standardoriginally intended for high-speed SANs connectingservers, disc arrays, and backup devices, also lateradapted to form the physical layer of Gigabit Ethernet.

Development work on Fibre channel started in 1988 and it wasapproved by the ANSI standards committee in 1994, running at100Mb/s. More recent innovations have seen the speed of FibreChannel SANs increase to 10Gb/s. Several topologies arepossible with Fibre Channel, the most popular being a numberof devices attached to one (or two, for redundancy) centralFibre Channel switches, creating a reliable infrastructurethat allows servers to share storage arrays or tape libraries.

One common use of Fibre Channel SANs is for high availabilitydatabaseq clusters where two servers are connected to onehighly reliable RAID array. Should one server fail, theother server can mount the array itself and continueoperations with minimal downtime and loss of data.

Other advanced features include the ability to have serversand hard drives seperated by hundreds of miles or to rapidlymirror data between servers and hard drives, perhaps inseperate geographic locations.

Fibre Channel Industry Association (FCIA).

Fibre Channel

A high-speed transport technology used to build storage area networks (SANs). Although Fibre Channel can be used as a general-purpose network carrying ATM, IP and other protocols, it has been primarily used for transporting SCSI traffic from servers to disk arrays. The Fibre Channel Protocol (FCP) serializes SCSI commands into Fibre Channel frames and uses IP for in-band SNMP network management (see SNMP). For more about storage networks, see SAN.

Specifications
Using singlemode or multimode fibers, Fibre Channel can be configured point-to-point (FC-P2P), as a switched topology (FC-SW) or in an arbitrated loop (FC-AL) with or without a hub, which can connect up to 127 nodes (see below). Transmission rates up to 12.75 Gbps in each direction are supported.

Fibre Channel uses the Gigabit Ethernet physical layer and IBM's 8B/10B encoding method, where each byte is transmitted as 10 bits. Fibre Channel provides both connection-oriented and connectionless services. Following are the class and functional levels. See FCIP, FCoE, IP storage and Director-class switch.

Connection-oriented services Class 1 With acknowledgment, full bandwidth Class 4 Virtual connections, QoS, fractional bandwidth Class 6 Uni-directional Connectionless services Class 2 With acknowledgment Class 3 Without acknowledgment Node levels FC-4 Translation between Fibre Channel and command sets that use it: HiPPI, SCSI, IPI, SBCCS, IP, IEEE 802.2, audio, video FC-3 Common services across multiple ports Port levels (FC-PH standard) FC-2 Framing and flow control FC-1 8B/10B encoding, error detection FC-0 Electrical and optical characteristics

Arbitrated Loop

The arbitrated loop is widely used and can connect up to 127 nodes without using a switch. All devices share the bandwidth, and only two can communicate with each other at the same time, with each node repeating the data to its adjacent node. TX means transmit, and RX means receive.

Switch Fabric

A switch fabric is the most flexible topology, enabling all servers and storage devices to communicate with each other. It also provides for a failover architecture in the event a server or disk array ceases to operate.

Point-to-Point

This is the simplest topology connecting two Fibre Channel devices that communicate at full bandwidth.