HSG80 ACS Solution Software Version 8.7 for Compaq Tru64 UNIX Installation and Configuration Guide

Glossary
–5HSG80 ACS Solution Software Version 8.7 for Compaq Tru64 UNIX Installation and
Configuration Guide
Glossary–5
data striping
The process of segmenting logically sequential data, such as a single
file, so that segments can be written to multiple physical devices
(usually disk drives) in a round-robin fashion. This technique is useful
if the processor is capable of reading or writing data faster than a single
disk can supply or accept the data. While data is being transferred from
the first disk, the second disk can locate the next segment.
DDL
Dual data link. The ability to operate on the CI bus using both paths
simultaneously to the same remote node.
device
See node and peripheral device.
differential I/O
module
A 16-bit I/O module with SCSI bus converter circuitry for extending a
differential SCSI bus. See also I/O module.
differential SCSI
bus
A bus in which a signal level is determined by the potential difference
between two wires. A differential bus is more robust and less subject to
electrical noise than is a single-ended bus.
DIMM
Dual inline Memory Module.
dirty data
The write-back cached data that has not been written to storage media,
even though the host operation processing the data has completed.
DMA
Direct Memory Access.
DOC
DWZZA-On-a-Chip. ASCSI bus extender chip used to connect a SCSI
bus in an expansion cabinet to the corresponding SCSI bus in another
cabinet (See DWZZA).
driver
A hardware device or a program that controls or regulates another
device. For example, a device driver is a driver developed for a specific
device that allows a computer to operate with the device, such as a
printer or a disk drive.
dual-redundant
configuration
A controller configuration consisting of two active controllers
operating as a single controller. If one controller fails, the other
controller assumes control of the failing controller devices.
dual-simplex
A communications protocol that allows simultaneous transmission in
both directions in a link, usually with no flow control.
DUART
Dual universal asynchronous receiver and transmitter. An integrated
circuit containing two serial, asynchronous transceiver circuits.