Glossary______________________________________________________________________________________. ATTO Technology FC2600, FCSW

2 Fibre Channel is a key technology for storage

Fibre Channel is a serial communications technology designed to transfer large amounts of data among a variety of hardware systems over long distances. It is a key technology for applications that require shared, high bandwidth access to storage.

Fibre Channel provides a logical, point-to-point, serial channel for the transfer of data between a buffer at a source device and a buffer at a destination device. It moves buffer contents from one port to another, without regard to the format or meaning of the data so different upper level protocols are able to run over Fibre Channel hardware.

The Fibre Channel architecture is structured as a hierarchical set of protocol layers. Defined within these layers are rules for signal interfaces, serial encoding and decoding, error control, frame format and communications protocols.

ATTO ExpressPCI Fibre Channel host adapters carry SCSI protocol over Fibre Channel.

Glossary

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Some terms used in the Fibre Channel industry are defined below. More information is available through the ATTO Technology website

(www.attotech.com), the Fibre Channel Industry Association

(www.fibrechannel.com), Cern (www.cern.ch), the Storage Area Networking Industry Association

(www.snia.org), and the Fibre Channel Consortium (www.iol.unh.edu/consortiums, click on FC).

Term

ANSI arbitrate arbitrated loop

Definition

American National Standards Institute process of selecting one L_Port from a collection of ports which ask for use of the arbitrated loop at the same time a loop topology (FC-AL) in which two or more ports are interconnected, but only two ports can communicate at one time; low-cost solution which may or may not use hubs and switches auto negotiation hardware senses and automatically responds depending on configuration

BER Bit Error Rate: a measure of transmission accuracy; the ratio of bits received in error to bits sent bit bus

Smallest unit of data a computer can process: a single binary digit with a value of either 0 or 1 a collection of unbroken signal lines used to transmit information from one part of a computer system to another; taps on the lines connect devices to the bus

Byte channel

CPU

CRC an ordered set of 8 bits a point-to-point link which transports data from one point to another

Central Processing Unit: the portion of the computer that actually performs computations

Cyclic Redundancy Check: an error-correcting code which calculates a numeric value for received and transmitted data; if no error has occurred during transmission, the CRC for both received and transmitted data should be the same destination address a value in the frame header of each frame which identifies the port in the node where the frame is being sent a program that allows a microprocessor to direct the operation of a peripheral device device driver

DMA Direct Memory Access: a way to move data from a storage device directly to RAM without using the CPU’s resources

DMA bus master Allows a peripheral to control the flow of data to and from system memory by block as opposed to allowing the processor to control the data by bytes (PIO or programmed I/O)

3 ATTO Technology ExpressPCI FCSW and FC 2600 Installation and Operation Manual

Term

fabric

FC

F_port

FL_port frame frame header full duplex half duplex host initiator device

L_port

LED

Definition

A Fibre Channel switch or two or more Fibre Channel switches interconnected to physically transmit data between any two N_Ports on the switch or switches

Fibre Channel

A port in the Fibre Channel fabric where a N_port may attach

A port in the Fibre Channel fabric where a NL_port may attach in an arbitrated loop an indivisible unit for transfer of information in Fibre Channel the first field in the frame containing the address and other control information about the frame a communication protocol which allows transmission in both directions at the same time a communication protocol which allows transmission in both directions, but only one direction at a time a processor, usually a CPU and memory, which communicates with devices over an interface

A component which originates a command a port in an arbitrated loop, either a NL_port or a FL_port

Light-emitting diode: a type of diode that emits light when current passes through it; visible LEDs are used as indicator lights on all sorts of electronic devices

LUN Logical Unit Number: an identifier for a logical unit (0-7) multi-mode fiber an optical fiber which can carry several beams of light at once

N_port

NL_ port a port attached to a node used with point to point or fabric configurations a port attached to a node in Fibre Channel arbitrated loop or fabric loop configuration originator an initiating device; a component which originates a command parity checking A method which verifies the accuracy of data transmitted over the SCSI bus by adding one bit in the transfer to make the sum of all the bits either odd or even (for odd or even parity); an error message occurs if the sum is not correct

PCI Peripheral Component Interconnect. Allows peripherals to be connected directly to computer memory, bypassing the slower ISA and EISA busses point-to-point port port address a topology where two ports communicate an access point in a device: see N_port, NL_port, etc.

also port number; the address, assigned by the PCI bus, through which commands are sent to a host adapter board port number receiver see port address the ultimate destination of data transmission; a terminal device scatter/gather

SCSI a device driver feature which allows the host adapter to modify a transfer data pointer so that a single host adapter can access many segments of memory, minimizing interrupts and transfer overhead

Small Computer Systems Interface: a processor-independent standard for system-level interface between a computer and intelligent devices including hard disks, floppy disks, CD-ROM, printers, scanners, etc. single-mode fiber an optical fiber with a small core which supports one wavelength (ray of light); the core radius is nearly equal to the wavelength of the source topology transceiver transfer rate logical layout of the parts of a computer system or network and their interconnections a transmitter/receiver module the rate at which bytes or bits are transferred, as in megabytes or gigabits per second

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