Redundant Array of Independent (or Inexpensive) Disks is a way of combining multiple hard disk drives to create an array that behaves like one large disk drive.
Arrays are designed for performance and fault tolerance. Spreading data across multiple disks improves access time, and using RAID's fault tolerance reduces the risk of losing data if one drive fails.
RAID is widely used in video applications becuase video often needs more throughput than one drive can sustain. Since video is so bandwidth-intensive, striping drives together (RAID 0) will help achieve the bandwidth required. More disks will yield greater bandwidth up to the limits of the interface. For example, the FireWire 400 bus tops out at 50MB/sec, while FireWire 800 will sustain around 80MB/sec. Because audio is transaction-based you will get decreased performance when usign striping (RAID 0) with an audio application. Audio file sizes tend to be smaller than video files so the time it takes for multiple drive heads to synchronize negates any bandwidth gains achieved in RAID 0. On the other hand, mirroring (RAID 1) can be beneficial in an audio application becuase it writes the data to two places at the same time. If one drive fails, the data is still present on the other.
| RAID Level | Description | Data Protection | Minimum Drives | Recommended Applications |
|---|---|---|---|---|
| 0 :: Striping | Data spread out across all disks. No data redundancy. | Low | 2 | Video production and editing |
| 1 :: Mirroring | Complete data redundancy. | Very high | 2 | Audio where data security is paramount |
| 3 :: Parallel transfer w/ parity | Data is written like striping. Parity data is stored on a separate hard drive. | Very high | 3 | Video production & editing with extra data security. |
| 5 :: Striping w/ parity | Data is written like striping. Parity data is stored on dedicated blocks within stripe set. | Very high | 3 | Video production & editing with extra data security. |