Compaq ProLiant Clusters HA/F100 Administrator's Manual page 197

Glossary-6 Compaq ProLiant Clusters HA/F100 and HA/F200 Administrator Guide
RAID
Redundant Array
of Inexpensive
Disks
Redundancy
Reliability
See Redundant Array of Inexpensive Disks
A method of using hard disk drives in an array to
provide data redundancy to increase system reliability
and performance. RAID is classified in the following
levels:
Data striping. This RAID level stripes
RAID 0
data across all drives of the array, but
does not incorporate a method to create
redundant data. RAID 0 does not provide
fault tolerance.
RAID Data striping with mirroring. This level
stripes data across the drives of the array
0+1
but duplicates the data through mirroring
to create a level of fault tolerance.
Drive mirroring. This level creates fault
RAID 1
tolerance by storing two sets of duplicate
data on a pair of disk drives.
Data guarding. This level involves the use
RAID 4
of a single, designated drive containing
parity data. If a drive fails, the controller
uses the data on the parity drive and the
remaining drives to reconstruct data from
the failed drive.
Distributed data guarding. This level
RAID 5
stores parity data across all the drives in
the array. Spreading the parity across all
the drives allows more simultaneous read
operations and higher performance than
data guarding (RAID 4).
The provision of multiple, interchangeable
components to perform a single function in order to
cope with failures and errors. A RAID set is
considered to be redundant when user data is recorded
directly to one member and all of the other members
include associated parity information.
The continuous integrity of a system (server, storage,
network, or cluster).