HP StorageWorks 2000 Modular Smart Array Reference Guide (481599-003, August 2008)

247
APPENDIX
B
RAID Levels
This appendix describes the different RAID levels that virtual disks in your system
can use.
Topics covered in this appendix are:
■ “Introduction” on page 247
■ “RAID Level Descriptions” on page 249
■ “Comparing RAID Levels” on page 252
■ “Mixing Disk Drive Models” on page 253
Introduction
The RAID controllers enable you to set up and manage virtual disks, whose storage
may be spread across multiple disk drives. This is accomplished through software
resident in the RAID controller. RAID (Redundant Array of Independent Disks)
refers to virtual disks in which part of the storage capacity may be used to store
redundant information. The redundant information enables the system to reconstruct
data if a drive in the virtual disk fails.
Hosts see each partition of a virtual disk, known as a volume, as a single disk drive.
A volume is actually a portion of the storage space on disk drives behind a RAID
controller. The RAID controller software makes each volume appear as a single,
very large disk drive. Depending on the RAID level used for a virtual disk, the disk
drive presented to hosts has advantages in fault-tolerance, cost, performance, or a
combination of these. This section explains the different RAID levels and the disk
requirements for each level.
Note – Choosing the right RAID level for your needs improves performance. The
following table includes examples of storage needs and appropriate RAID levels.