HP StorageWorks HSG60 and HSG80 Array Controller and Array Controller Software Command Line Interface Reference Guide (EK-G80CL-RA. C01, March 2005)

Glossary
331HP StorageWorks HSG60 and HSG80 Array Controller and Array Controller Software
Command Line Interface Reference Guide
read caching
A cache management method used to decrease the subsystem response time to a read
request by allowing the controller to satisfy the request from the cache memory rather than
from the disk drives.
read-ahead caching
A caching technique for improving performance of synchronous sequential reads by
prefetching data from disk.
reconstruction
The process of regenerating the contents of a failed member’s data. The reconstruct process
writes the data to a spareset disk and then incorporates the spareset disk into the mirrorset,
striped mirrorset, or RAIDset from which the failed member came. See also regeneration.
reduced
A term that indicates that a mirrorset or RAIDset is missing one member because the
member has failed or is physically removed.
redundancy
The provision of multiple interchangeable components to perform a single function in order
to cope with failures and errors. A RAIDset is considered to be redundant user data is
recorded directly to one member and all of the other members include associated parity
information.
regeneration
(1) The process of calculating missing data from redundant data. (2) The process of
recreating a portion of the data from a failing or failed drive using the data and parity
information from the other members within the storageset.
The regeneration of an entire RAIDset member is called reconstruction. See also
reconstruction.
remote copy
A feature intended for disaster tolerance and replication of data from one storage subsystem
or physical site to another subsystem or site. Remote copy also provides methods of
performing a backup at either the local or remote site. With remote copy, user applications
continue to run while data movement goes on in the background. Data warehousing,
continuous computing, and enterprise applications all require remote copy capabilities.
remote copy set
A bound set of two units, one located locally and one located remotely for long distance
mirroring. The units can be a single disk, or a storageset, mirrorset, or RAIDset. A unit on
the local controller is designated as the “initiator” and a corresponding unit on the remote
controller is designated as the “target.” See also association set.