Enabling The Enhanced Serial Ata Hard Disk Driver Interface; Ahci And Native Command Queueing; Raid 0 And Raid 1 - IBM SurePOS 700 Series Operating System Installation Manual

Updated October, 2007

Enabling the enhanced Serial ATA hard disk driver interface

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AHCI and Native Command Queueing

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RAID 0 and RAID 1

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1. Dependant upon the NCQ feature becoming the standard in the industry.
IBM SurePOS 700 Models 742, 782, 723, 743, and 783 have an embedded Serial
ATA (SATA) controller with Advanced Host Controller Interface (AHCI) and
Redundant Array of Independent Disks (RAID) support. To take advantage of either
of these features, they must be enabled prior to operating system installation and
the driver must be installed during the installation of the operating system. Once the
operating system is installed, the mode of operation can not be changed without
reinstalling the operating system.
Models 742, 782, 723, 743, and 783 can enable the AHCI mode of operation, if
they have a hard drive installed. Currently, AHCI mode does not provide any
measurable performance benefit with the standard hard disk drive installed in
Models 742 or 782. However, the Native Command Queueing (NCQ) is becoming a
standard feature on hard disk drives and will provide a performance benefit, if the
AHCI controller is enabled.
IBM will not provide a replacement or an upgrade of customer hard disk drives
should this feature become standard. If the application requires a drive with NCQ
support, you should submit an RPQ through your IBM Sales Representative. This
information is provided to allow customers to prepare OS/Application images
properly for future use.
Enabling the native RAID application requires a Models 742, 782, 723, 743, and
783 with one or two hard disk drives. To take full advantage of the RAID function,
you must install two drives. With two drives installed, the native RAID function
supports both RAID 0 and RAID 1. For two drive implementations, RAID 1 is the
recommended mode of operation.
Enabling RAID and using the RAID driver is the recommended mode of operation
for one and two drive configurations. The RAID mode of operation will take
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advantage of NCQ with single drive systems. Also, single drive systems with RAID
enabled can be later upgraded to two drive systems by just adding the second hard
disk drive, booting the OS and using the RAID utility to create an array without
requiring the OS or applications to be reinstalled.
RAID 0 (striping)
Increases the system hard disk performance, however the overall reliability
is reduced as a single drive failure will result in total data loss.
RAID 1 (mirroring)
Does not increase performance, but the drives are maintained as identical
copies. If one hard disk drive experiences a hardware failure, the system
will continue to function until the failing drive can be serviced.
Note: RAID does not prevent or eliminate errors caused by OS issues, application
failures, corrupt files, viruses and other software induced problems that are
often perceived as hard drive failures. RAID 1 can only minimize the impact
of a single hard drive hardware failure.
Chapter 1. Preparing for the installation
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