RAID requires at least two hard drives to implement.
The drive controllers on many modern motherboards have built-in support for Redundant Arrays of Independent Disks, enabling computer users to implement RAID on their computers without purchasing RAID controller cards. Although there are many types -- or "levels" -- of RAID, the two most common are RAID 0 and RAID 1.
RAID 0 and RAID 1
RAID is a system of distributing data across multiple hard drives connected to the same controller. RAID 0 and RAID 1 distribute the data differently; with RAID 0, the data is split evenly among the hard drives in the array. For example, in a two-drive array, half of the total data is stored on each drive. RAID 0 is also known as "striping." With RAID 1, each hard drive in the array stores the same data. RAID 1 is also known as "mirroring." RAID 0 and RAID 1 require at least two hard drives, while the maximum number of drives is determined by the controller. If the hard drives are not of equal capacity, the smallest-capacity drive in the array determines the total size of the array.
RAID 0 Benefit
Because RAID 0 splits the work evenly among multiple hard drives when reading or writing data, it increases the speed of the computer's storage subsystem when transferring large files. RAID 0 can nearly double a computer's performance when reading or writing contiguous data. However, random read and write operations -- such as starting the operating system or loading a game level -- show less of an improvement, and can in some cases be slower. Applications that can benefit from RAID 0 include video and audio production. In these applications, it is often necessary to open, modify and save files more than 1GB.
RAID 0 Drawback
A RAID 0 array is destroyed if any of its hard drives stops working, resulting in the loss of all data. In addition, a two-drive array is twice as likely as a single drive to fail. Because of the possibility of failure, it is important to maintain a data backup when using a RAID 0 array.
RAID 1 Benefit
Because RAID 1 stores the same data on every hard drive in the array, it increases the reliability of a computer's storage subsystem. For the data in a RAID 1 array to be lost, all of the drives in the array must fail. When one drive fails, the controller triggers the computer to display a warning notifying you. When you open your computer and replace the faulty drive, the controller rebuilds the array automatically.
RAID 1 Drawback
RAID 1 reduces the computer's usable storage space. If you have a RAID 1 array with two 1 TB hard drives, for example, the total amount of file storage space is 1 TB rather than 2 TB because all of the data written to the array is stored on both drives.
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