ATTO Technology VT-Class manual Appendix a Glossary, Fibre Channel technology, SAN technology

Appendix A Glossary

The following terms are only a few examples of the language used for Fibre Channel, SCSI and storage systems. For more information, visit the websites of these professional organizations: the Fibre Channel Industry Association www.fibrechannel.org; the Fibre Channel Consortium www.iol.unh.edu/consortiums/index.html click on Fibre Channel; the Storage Area Networking Industry Association www.snia.org, or SCSI Trade Association www.scsita.org.

Fibre Channel technology

Fibre Channel (FC) is a serial communication interface designed to transfer large amounts of data among a variety of hardware systems over long distances. It is becoming 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, allowing different upper level protocols to run over the Fibre Channel connection.

The Fibre Channel architecture is 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. Fibre Channel provides a range of implementation possibilities and purposely isolates the transmission medium from the control protocol so that each implementation may use the technology best suited to the application.

Fibre Channel arbitrated loop (FC-AL) technology allows 127 systems and devices to be distributed over

a range of up to 10 kilometers running at speeds of 1 gigabit/sec. Multiple FC-AL loops can be connected via a fabric switch topology to extend the range.

SAN technology

A Storage Area Network (SAN) is a shared storage architecture. SANs connect computers and storage devices for online data access. Each connected system can directly access any attached storage device. A SAN maintains greater fault tolerance and load balancing by supporting server clustering and fail-over (the ability for one server to take over for another in the event of a failure.

SCSI protocol

SCSI (pronounced scuzzy) stands for Small Computer System Interface, a processor-independent standard for system-level interface between a computer and SCSI devices such as hard disks, CD-ROM and printers, and to other computers and local area networks.

The protocol has many standards specifying data transfer rates, data width and speeds which allow SCSI devices to exchange data and control signals with a computer's CPU. Each device connected to a SCSI bus must have a different SCSI ID.

Term	Definition
arbitrate	process of selecting one L_Port from a collection of ports which ask for use of the arbitrated
	loop at the same time
arbitrated loop	a loop topology in which two or more ports are interconnected, but only two ports can
	communicate at one time
ATA	Advanced Technology Attachment: A disk drive interface standard, formerly called IDE; the
	ATA specification deals with the power and data signal interface of an integrated disk
	controller and drive
auto negotiation	hardware senses and automatically responds depending on configuration
CLI	Command Line Interface: used by applications and advanced users to perform diagnostic
	or configuration tasks; access is available through a computer terminal or terminal emulator
	via connections to the RS-232 port or the optional Ethernet management services card via
	the local area network using Telnet
fabric	A FC switch or two or more FC switches interconnected to physically transmit data between
	any two N_Ports on a switch or switches

A-i

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