Redundant Array Of Inexpensive Disks (Raid)

A redundant array of inexpensive disks (RAID) is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both.

This definition explains what a RAID is and how it works. RAID combines multiple physical disk drive components into a single logical unit. There are different ways to configure a RAID system, but the most common layouts are called levels. The various RAID levels differ in their approaches to combining the drives and achieving redundancy. The most common RAID levels are: RAID 0: Striping without parity or mirroring. Provides improved performance and additional storage capacity over a single drive, but no redundancy. If one drive fails, all data is lost. RAID 1: Mirroring without striping. All data is written identically to two (or more) drives, providing full redundancy.

Read performance is improved because any single drive can be used to satisfy a read request. Write performance is the same as for a single drive because all write requests must be sent to all drives in the array. Additional drives can be added to improve read performance further, but this has no effect on write performance or capacity. RAID 5: Striping with distributed parity information across all drives in the array. Requires at least three drives.