The term “hardware RAID” refers to using dedicated hardware to accomplish RAID. This is typically done by adding a RAID controller to an expansion port on the motherboard. The RAID controller will have it own processing controllers to handle the RAID.

Servers that are designed for multiple disk drives usually have a RAID controller card that controls the RAID. The RAID controllers are configured during the boot up process of the server, before the operating system is loaded. When the operating system loads on the server, it sees the RAID array as a it would any other disk drive volume, and is not aware of any RAID configurations done by the RAID controller.

There are many advantages to using hardware RAID. Because the controller has its own processing chip, this frees up the computer CPU from having to perform RAID operations. The controller can also provide large caching areas helping to improve the read and write performance. Also because the RAID controller is configured before the operating system boots, the operating system itself can be installed within the RAID volume.