HSG80 ACS Solution Software V8.6 for IBM AIM Installation and Configuration Guide

Glossary–4 HSG80 ACS Solution Software Version 8.6 for IBM AIX Installation and Configuration Guide
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.
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.
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.
ECB External cache battery. The unit that supplies backup power to the cache
module in the event the primary power source fails or is interrupted.
ECC Error checking and correction.
EDC Error detection code.