Introduction; Mirroring And Parity; Disk Striping; Basics Of Raid Technology - Compaq dc5750 - Microtower PC User Manual

Introduction

A RAID (Redundant Array of Independent Disks) is a data storage scheme that uses two or more drives
accessed in combination to improve fault tolerance. Initially used with servers, desktop PCs are increas-
ingly using RAID controller and extra ATA or SCSI disks. Newer system boards often have RAID control-
lers.
RAID technology takes advantage of Serial Advanced Technology Attachment (SATA) and the integration
of RAID into ATI's Radeon Xpress 1 150 chipset with SB600 technology. The HP Compaq dc5750 Business
PC products incorporate RAID drive support through factory configurations. This white paper provides a
basic overview of RAID technology, supported factory configurations of HP Compaq dc5750 Business
PCs, and other supported RAID configurations.

Mirroring and Parity

Fault tolerance is achieved by mirroring or parity. Mirroring is 100% duplication of the data on two drives
(RAID 1). Parity is used to calculate the data in two drives and store the results on a third drive (RAID 5).
After a failed drive is replaced, the RAID controller automatically rebuilds the lost data from the other two
drives. RAID systems may have a spare drive (hot spare) ready and waiting to be the replacement for a
drive that fails.

Disk Striping

RAID improves performance by disk striping, which interleaves bytes or groups of bytes across multiple
drives, so more than one disk is reading and writing simultaneously.

Basics of RAID Technology

Definitions

RAID Definitions
Table 1 Basic
ATA Advanced Technology Attachment.
BIOS Basic Input/Output System, also known as system ROM.
Chipset Term used to define a collection of integrated components required to make a PC function.
HDD Hard disk drive.
IDE Integrated Drive Electronics.
INF Information file (.inf) used by Microsoft operating systems that support the Plug & Play feature.
When installing a driver, this file provides the operating system needed information about driver
filenames, driver components, and supported hardware.
Migration Term used to describe the movement of data from one configuration or usage model to another.
2