Q. Should I use Advanced Host Controller Interface (AHCI) or RAID mode in my BIOS settings?

A. AHCI provides enhanced features for SATA drives, including native command queuing, (which lets drives accept and reorder multiple commands for performance), hot plugging of devices, and staggered spin up of multiple hard drives at boot time. AHCI mode enables these features but in most cases requires the OS use a special driver, as opposed to IDE mode, which uses the Microsoft driver that's part of the OS.

In addition, some motherboards have a RAID mode, which includes all the features of AHCI mode but also adds support for configuring highly available sets of disks. You should always choose RAID instead of AHCI, as it gives increased flexibility for the future, even if you don't intend to use RAID initially. By choosing RAID mode, you'll avoid configuration problems if you later want highly available disks.

Related Reading:
Check out hundreds more useful Q&As like this in John Savill's FAQ for Windows. Also, watch instructional videos made by John at ITTV.net.
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