HP Dc5850 AHCI and RAID on HP Compaq dc5850 Business PCs - 2nd Edition - Page 2

Introduction, Basics of AHCI and RAID Technology - desktop pc

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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 increasingly using RAID controllers and extra ATA or SCSI disks. Newer system boards often have RAID controllers. The HP Compaq dc5850 Business PC takes advantage of Serial Advanced Technology Attachment (SATA) and the integration of RAID into AMD's RS780 and SB700 chipsets. The HP Compaq dc5850 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 dc5850 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.MBR = Master Book Record Basics of AHCI and RAID Technology Definitions Table 1 Basic AHCI and RAID Definitions AHCI ATA BIOS Chipset HDD IDE Advanced Host Controller Interface, a specification for hardware and software, is a register interface for SATA, intended to add higher speed, NCQ and other features. Advanced Technology Attachment. Basic Input/Output System, also known as system ROM. Term used to define a collection of integrated components required to make a PC function. Hard disk drive. Integrated Drive Electronics. 2

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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 controllers and extra ATA or SCSI disks. Newer system boards often have RAID control-
lers.
The HP Compaq dc5850 Business PC takes advantage of Serial Advanced Technology Attachment
(SATA) and the integration of RAID into AMD’s RS780 and SB700 chipsets. The HP Compaq dc5850
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 dc5850
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.
MBR = Master Book Record
Basics of AHCI and RAID Technology
Definitions
Table 1
Basic AHCI and
RAID Definitions
AHCI
Advanced Host Controller Interface, a specification for hardware and software, is a register
interface for SATA, intended to add higher speed, NCQ and other features.
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.