Veritas™ Volume Manager Administrator's Guide

Disk arrays

Performing I/O to disks is a relatively slow process because disks are physical devices that require time to move the heads to the correct position on the disk before reading or writing. If all of the read or write operations are done to individual disks, one at a time, the read-write time can become unmanageable. Performing these operations on multiple disks can help to reduce this problem.

A disk array is a collection of physical disks that VxVM can represent to the operating system as one or more virtual disks or volumes. The volumes created by VxVM look and act to the operating system like physical disks. Applications that interact with volumes should work in the same way as with physical disks.

Figure: How VxVM presents the disks in a disk array as volumes to the operating system shows how VxVM represents the disks in a disk array as several volumes to the operating system.

Figure: How VxVM presents the disks in a disk array as volumes to the operating system

Data can be spread across several disks within an array, or across disks spanning multiple arrays, to distribute or balance I/O operations across the disks. Using parallel I/O across multiple disks in this way improves I/O performance by increasing data transfer speed and overall throughput for the array.