Compaq HSZ80 manual GL-8Glossary, Operation

GL–8Glossary
I/O module	A 16-bit SBB shelf device that integrates the SBB shelf with either an 8-bit
	single ended, 16-bit single-ended, or 16-bit differential SCSI bus.
I/O operation	The process of requesting a transfer of data from a peripheral device to
	memory (or vice versa), the actual transfer of the data, and the processing
	and overlaying activity to make both of those happen.
JBOD	Just a Bunch of Disks. Describes a group of single-device logical units.
LBN	Logical Block Number.
LED	Light Emitting Diode.
local connection	A connection to the subsystem using either its serial maintenance port or the
	host’s SCSI bus. A local connection enables you to connect to one subsystem
	controller within the physical range of the serial or host SCSI cable.
local terminal	A terminal plugged into the EIA-423 maintenance port located on the front
	bezel of the controller. See also maintenance terminal.
logical bus	A single-ended bus connected to a differential bus by a SCSI bus signal
	converter.
logical unit	A physical or virtual device addressable through a target ID number. LUNs
	use their target’s bus connection to communicate on the SCSI bus.
logical unit number	A value that identifies a specific logical unit belonging to a SCSI target ID
	number. A number associated with a physical device unit during a task’s I/O
	operations. Each task in the system must establish its own correspondence
	between logical unit numbers and physical devices.
LRU	Least Recently Used. A cache term used to describe the block replacement
	policy for read cache.
Mb/s	Megabits per second. Approximately one million (106) bits per second.