HP StorageWorks HSG60 and HSG80 Array Controller and Array Controller Software Troubleshooting Guide (EK-G80TS-SA. C01, March 2005)

Glossary
295HSG60 and HSG80 Array Controller and Array Controller Software Troubleshooting Guide
RAIDset
A specially developed 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. RAIDsets are sometimes referred to as
parity RAIDs or RAID level 3/5 storagesets.
RAM
Random access memory.
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 failed member 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
Indicates that a mirrorset or RAIDset is missing one member because the member failed or
was 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 if 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 by 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.