Specifications

GL–5
Compaq HSG80 Array Controller ACS Version 8.4 Configuration and CLI Reference 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’s 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. An NCR53C120 SCSI 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’s devices.