Hitachi 9900 Series - Manual (Page 72)

Lightning 9900 ™ Series
The Lightning 9900 ™ Series was announced in June 2000 (Lightning 9960 ™ ) and
November (Lightning 9910 ™ ). It represents a major advance in enterprise-class storage
systems with its Hierarchical Star Network switched internal architecture, which
provides for many times more simultaneous transfers to and from the host compared
to shared bus architectures.
Logical Unit
The SCSI term for a logical disk drive.
Logical Unit Number
See LUN.
Logical Volume
The storage medium associated with a logical disk drive. A logical volume typically
resides on one or more storage devices. A host system sees a logical volume as a
physical volume, although it does not correlate directly with a physical disk drive.
LUN
Logical Unit or Logical Unit Numbers. A SCSI term for the field in an identifying
message that is used to select a logical unit on a given target.
LPAR
Logical partition is an IBM ESA/390 ® term for a set of functions that create the
programming environment that is defined by the ESA/390 ® architecture. ESA/390 ®
architecture uses this term when more than one LPAR is established on an ESA/390
server. An LPAR is conceptually similar to a virtual machine environment except that
the LPAR is tied to one or more physical processors in a tightly coupled multiprocessor
system. Also the LPAR does not depend on an operating system to create the virtual
machine environment.
LUSE
LUN Size Expansion feature. This Lightning 9900 ™ feature allows standard-size LUNs
to be combined to create larger LUNs.
LRU
Least Recently Used. A policy for a caching algorithm that chooses to remove the data
from cache which has the longest elapsed time since its last access. Least Recently Used
algorithms are used in all major caching systems. The Lightning 9900
™ Series’ LRU
scheme keeps a table (in separate non-volatile memory) that chronicles the frequency
of use of data in cache memory.
MAN
Metropolitan Area Networks. Networks within a metropolitan area, which might for
example, be used for a city government.
63
Glossary