Compaq StorageWorks HSG60 ACS Solution Software V8.6 for Compaq Tru64 UNIX Installation and Configuration Guide

Glossary–15
RAID level 5 A RAID storageset that, unlike RAID level 3, stores the parity information
across all of the disk drives within the storageset. See also RAID level 3.
RAID level 3/5 A RAID storageset that stripes data and parity across three or more members
in a disk array. A RAIDset combines the best characteristics of RAID level 3
and RAID level 5. A RAIDset is the best choice for most applications with
small to medium I/O requests, unless the application is write intensive. A
RAIDset is sometimes called parity RAID.
RAIDset See RAID level 3/5.
RAM Random access memory.
read ahead caching A caching technique for improving performance of synchronous sequential
reads by prefetching data from disk.
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.
reconstruction The process of regenerating the contents of a failed member data. The
reconstruct process writes the data to a spareset disk and incorporates the
spareset disk into the mirrorset, striped mirrorset, or RAIDset from which the
failed member came. See also regeneration.
reduced Indicates that a mirrorset or RAIDset is missing one member because the
member has failed or has been 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 when 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.
request rate The rate at which requests are arriving at a servicing entity.
RFI Radio frequency interference. The disturbance of a signal by an unwanted
radio signal or frequency.