RAID User Guide

4 Intel Rapid Storage Technology
features
Intel Rapid Storage Technology supports the following Recovery features.
Advanced Host Controller Interface
The Advanced Host Controller Interface (AHCI) is a specification that allows the storage driver to
enable advanced SATA features such as Native Command Queuing and hot plug capability. AHCI
must be enabled in the system BIOS for these features to apply (see
Enable RAID through the
system BIOS (f10) on page 13). AHCI is enabled by default on supported HP Business computers.
Native Command Queuing
A read/write drive head writes data to an HDD platter in concentric circles (tracks) based on the order
in which the write request was received. Because applications rarely request data in the same order
that it was written to the platter, long delays (latency) would result if the drive head had to locate data
in the exact order that the HDD receives read requests. Native Command Queuing (NCQ) allows
SATA HDDs to accept multiple commands and change their execution order to improve performance.
This is analogous to the way an elevator reorders floor requests to minimize travel time and
mechanical wear. Similarly, NCQ reduces the latency and unnecessary drive head movement
required to execute multiple outstanding read/write requests, resulting in increased performance and
reliability. NCQ requires support from the system BIOS, SATA controller, and controller driver.
Hot plug capability
Hot plug capability allows the SATA recovery HDD to be removed or inserted while the computer is
running. Hot plug capability is supported when the recovery HDD is connected to the eSATA port or
located in the docking station's SATA-swappable bay. For example, the recovery HDD in the docking
station's SATA-swappable bay can be removed while the computer is running if you need to
temporarily insert an optical drive in the bay. Hot plug capability also allows you to dock and undock
the computer at any time.
10 Chapter 4 Intel Rapid Storage Technology features