HP StorageWorks XP24000/XP20000 Disk Array Owner Guide (AE131-96081, September 2010)

Glossary
ACP Array control processor.
AL Arbitrated loop.
AL-PA Arbitrated loop physical address.
allocation The ratio of allocated storage capacity versus total capacity as a percentage.
Allocated storage refers to those logical devices (LDEVs) that have paths assigned
to them. Allocated storage capacity is the sum of the storage of these LDEVs.
Total capacity is the sum of the capacity of all LDEVs on the disk array.
array group A group of four or eight physical hard disk drives (HDDs) installed in an XP array
and assigned a common RAID level. RAID1 array groups consist of four (2D+2D)
or eight HDDs (4D+4D). RAID5 array groups include a parity disk, but also
consist of four (3D+1P) or eight HDDs (7D+1P). All RAID6 array groups are
made up of eight HDDs (6D+2P).
BC HP Business Copy. An HP StorageWorks application that lets you maintain up
to nine local copies of logical volumes on the disk array.
cache Very high speed memory that is used to speed I/O transaction time. All reads
and writes to the XP array family are sent to the cache. The data is buffered there
until the transfer to/from physical disks (with slower data throughput) is complete.
The benefit of cache memory is that it speeds I/O throughput to the application.
The larger the cache size, the greater the amount of data buffering that can occur
and the greater throughput to the applications.
XP arrays support a range of cache memory. In the event of power loss, battery
power maintains the contents of cache for a specified time period.
CAS Customer Access System.
CHA Channel adapter. A device that provides the interface between the array and
the external host system. Occasionally, this term is used synonymously with the
term channel host interface processor (CHIP).
CHIP Channel host interface processor. Synonymous with the term CHA.
CHP Channel processor. The processors located on the CHA. Synonymous with CHIP.
command device A volume on the disk array that accepts HP StorageWorks Continuous Access
or HP StorageWorks Business Copy control operations which are then executed
by the array.
Continuous Access The HP StorageWorks XP Continuous Access program, which enables you to
replicate data stored on a local disk array to a remote disk array.
control unit To organize the storage space attached to the DKC, you can group similarly
configured LDEVs with unique CU images. CUs are numbered sequentially. The
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