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GL–8
Glossary
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 (10
6
) bits per second.
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