Sun Microsystems StorageTek 96257 - Manual (Page 93)

96257 Sun Confidential: Internal Only C-93
Revision A
J
jack. A connector into which a plug is inserted.
JBOD. Just a Bunch of Disks. A term used to describe a
data storage cabinet that contains only disk storage de-
vices, without an internal control unit. A JBOD typically
attaches to a host system, which provides control func-
tions and intelligence.
journal. A log (stored in a dataset) that contains a record
of completed work and changes to the control dataset
since the last backup was done.
K
Kb. Kilobit. A unit of data capacity equivalent to 1024
(10
3
) bits.
KB. Kilobyte. A unit of data capacity equal to 1024 (10
3
)
bytes. Also abbreviated kbyte, Kbyte.
Kbps. Kilobits per second (thousand bits per second).
KBps. Kilobytes per second (thousand bytes per sec-
ond).
kg. Kilogram. A unit of weight equal to one thousand
grams (2.2 pounds).
kHz. Kilohertz. A unit of frequency equal to 1000 cycles
per second.
km. Kilometer. A unit of distance equal to one thousand
meters (0.62 mile).
L
LAN. Local area network. A grouping of two or more
computers connected by cable which use an operating
system and application software to allow direct sharing
of hard disks, printers, files, etc.
LBA. See logical block address.
LCD. Liquid crystal diode. Also called liquid crystal dis-
play. A display technology that uses rod-shaped mole-
cules (liquid crystals) that flow like liquid and bend light.
LED. Light-emitting diode. A semiconductor chip that
emits visible or infrared light when activated.
link. (1) A point-to-point pair of conductors (optical fi-
bers) that physically interconnects a control unit and a
channel, a channel and a dynamic switch (e.g., a direc-
tor), a control unit and a dynamic switch, or, in some cas-
es, a dynamic switch and another dynamic switch. (2) In
an ESCON environment, the physical connection and
transmission medium used between an optical transmit-
ter and optical receiver. A link consists of two conductor
paths, one for sending and the other for receiving, pro-
viding a duplex communication path.
link address. An address assigned during IML that iden-
tifies a channel or control unit and allows it to send and
receive frames, and to perform I/O operations.
LMS. Library Management Software.
LMU. Library Management Unit.
load. In VSM, the average percentage of VTSS disk ar-
ray cylinder space that must be relocated to create emp-
ty array cylinders in the subsystem.
logical. In VTSS, a view or description of storage com-
ponents (cylinders, devices, tracks, volumes, etc.) that is
dynamic and independent of the physical location of
those components. Contrast with functional, physical.
logical array. A grouping of devices into an array inde-
pendent of physical device locations.
logical block address (LBA). A four-byte number used
to identify a logical block on a SCSI drive. The address
range is 0 to n, where n equals the number of blocks on
a drive.
logical path. (1) A logical connection between a channel
image and a control unit image. Every logical path has
an associated physical path, but a physical path may
‘contain’ multiple logical paths. VSM4-VTSS can have up
to 512 logical paths to 1 to 28 hosts. (2) A relationship
between a channel and control unit that designates the
physical path to be used for device-level communication
between each entity, defined by a link address assigned
to each entity.
LOGREC. Logical record. A data set maintained by a
host system containing records of usage and errors en-
countered for various system components, primarily pe-
ripheral devices.
logical-to-physical mapping. The defined relationship
between logical devices and specific physical devices.
See mapping. See also fixed mapping, dynamic map-
ping.
logical sector recovery. A process of reading remaining
(n - 1) physical sectors at a location within a parity group
and combining these sectors, using parity generation, to
produce the otherwise unreadable content of the nth
physical sector, thereby allowing recovery of the logical
sector involved. See also functional track recovery.
L_Port. Loop port. Also written as L_PORT.
LSF. Log-Structured File.
LTO. Linear Tape-Open.
LUN. Logical unit. The basic structure created in a RAID
subsystem to retrieve and store data, comprised of an
array of physical drive modules. The operating system
views a LUN as a single drive rather than as the group of
drives that comprise the array.
LPAR. Logical partition.
LSM. Library Storage Module.
M
machine address. An address that is permanently as-
signed to a specific storage location in a computer, by
the maker of the machine.
mainframe. A large computer with ability to support hun-
dreds or thousands of users simultaneously.
mapping. The way in which locations of functional, logi-
cal, and physical objects are related to one another.
There are two types of mapping: functional-to-logical,
and logical-to-physical; each can be either dynamic or
fixed. See also dynamic mapping, fixed mapping.
MAT. See media acceptance test.
Mb. Megabit. A unit of data capacity equal to one million
(1,000,000 or 10
6 ) bits. One megabit is equal to one
thousand kilobytes.
MB. Megabyte. A unit of data capacity equal to one mil-
lion (1,000,000 or 10
6 ) bytes. One megabyte is equal to
one thousand kilobytes. Contrast with byte, gigabyte, ki-
lobyte, petabyte, terabyte.
Mbps. Megabits per second.
MBps. Megabytes (million bytes) per second. A measure
of the data transmission rate through a data path.