Technical data

GL–4 Glossary
DAEMON Pronounced “demon.” A program usually associated with a UNIX systems
that performs a utility (housekeeping or maintenance) function without
being requested or even known of by the user. A daemon is a diagnostic and
execution monitor.
data center cabinet A generic reference to large DIGITAL subsystem cabinets, such as the
SW600-series and 800-series cabinets in which StorageWorks components
can be mounted.
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.