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Chapter 4
SV-2003-X2 Server
Part Number: 1006446 Page 65 of 72
Version 1.0. 10/30/07
6 RAID
RAID is an acronym for Redundant Array of
Inexpensive (or Independent) Disks. This
section provides a high-level overview that
defines RAID, the advantages and
disadvantages of various RAID levels, and
guidelines to observe when implementing
RAID.
6.1 RAID Defined
RAID is a way of storing data on two or more
physical disks for the purpose of redundancy,
improved performance, or both. The combined
physical disks make up what is called an array.
This array appears on the host system as one
disk. For example, if you have physical disk 1
and physical disk 2, those two disks appear to
the host system as one disk.
RAID consists of different levels, which
determine how the data is placed in the array.
Each RAID level has specific data protection
and system performance characteristics. The
following are commonly used SCSI RAID
levels:
1. RAID Level 0: Striping, good performance, no
redundancy
2. RAID Level 1: Mirroring, one-to-one
redundancy
3. RAID Level 5: Striping with parity striped
across all drives; offers performance and
redundancy
4. RAID Level 10: Mirroring and striping; best
redundancy and best performance
5. RAID Level 50: Parity striped across all drives
in a mirrored set; redundancy and performance
You can manage RAID arrays with a RAID
controller (hardware RAID) or with software
alone (software RAID).