HP StorageWorks XP24000/XP20000 Disk Array Site Preparation Guide (AE002-96055, September 2010)

Glossary
AL Arbitrated loop.
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.
AL-PA Arbitrated loop physical address.
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).
Business Copy The HP StorageWorks XP Business Copy software program, which enables you
to maintain up to nine internal copies of logical volumes on the disk array.
C-Track The HP StorageWorks XP Continuous Track remote support solution, which detects
internal hardware component problems on a disk array and automatically reports
them to the HP STC (Storage Technology Center). C-Track also enables STC
remote diagnosis of the array. There are Internet-based and modem-based C-Track
solutions.
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 up to 36 hours.
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).
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 logical devices (LDEVs) with unique control unit images (CUs). CUs
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