Introduction; Mirroring And Parity; Disk Striping; Basics Of Raid Technology - HP Blade dc72 User Manual

Introduction

RAID (Redundant Array of Independent Disks) is a category of hard drives that employ two or more drives
in combination for fault tolerance and performance. Initially used with servers, desktop PCs are increas-
ingly using RAID by adding a RAID controller and extra IDE or SCSI disks. Newer system boards often
have RAID controllers.
RAID technology takes advantage of Serial Advanced Technology Attachment (SATA) and the integration
of RAID into the Intel Q965/ICH8-D0 chipset. The HP Compaq dc7700 and dx7300 Business PC prod-
ucts are the first business desktops to incorporate RAID drive support through factory configurations. This
white paper provides a basic overview of RAID technology, supported factory configurations of HP Com-
paq dc7700/dx7300 Business PCs, other supported RAID configurations, and basic instructions on how
to migrate non-RAID to RAID configurations in the field.

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.
ICH Intel Input/Output Controller Hub, inside this component resides the mass storage controller.
ICH is part of the Intel Q965 chipset.
IDE Integrated Drive Electronics.
3