VERITAS Volume Manager 3.1 Reference Guide

112 Chapter3
Disk Arrays
Disk Array Overview
Figure 3-2 RAID-3 Disk Array
The user data is striped across the data disks. Each stripe on the parity
disk contains the result of an exclusive OR (XOR) procedure done on the
data in the data disks. If the data on one of the disks is inaccessible due
to hardware or software failure, data can be restored by XORing the
contents of the remaining data disks with the parity disk. The data on
the failed disk can be rebuilt from the output of the XOR process.
RAID-3 typically uses a very small stripe unit size (also historically
known as a stripe width ), sometimes as small as one byte per disk
(which requires special hardware) or one sector (block) per disk.
Disk 1
Disk 2
Disk 3
Disk 4
Virtual
Disk(s)
Operating System
Controller
Parity
Disk
Data Disks