Scsi Is A Key Technology For Storage; Glossary - ATTO Technology UL3D Installation And Operation Manual

2 SCSI is a key technology for storage

SCSI is a serial communications technology designed to transfer large amounts of data between a
variety of hardware systems over long distances. It is a key technology for applications that require
shared, high bandwidth access to storage.
SCSI 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 SCSI
hardware.
The SCSI 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 Express PCI SCSI host adapters carry SCSI protocol over SCSI.

Glossary

Some terms used in the SCSI industry are defined below. More information is available through the
ATTO Technology website (www.attotech.com), and the SCSI Consortium
(www.iol.unh.edu/consortium).
Term
ANSI
auto negotiation
BER
bit
byte
CRC
host
initiator device
LED
originator
receiver
SCSI
3 ATTO Technology ExpressPCI Ultra3 SCSI Host Adapters Installation and Operation Manual
Definition
American National Standards Institute
hardware senses and automatically responds depending on configuration
Bit Error Rate: a measure of transmission accuracy; the ratio of bits received in
error to bits sent
Smallest unit of data a computer can process: a single binary digit with a value of
either 0 or 1
an ordered set of 8 bits
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.
a processor, usually a CPU and memory, which communicates with devices over
an interface
A component which originates a command
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.
an initiating device; a component which originates a command
the ultimate destination of data transmission; a terminal device
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.