RAID (redundant array of independent disks)

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RAID (originally redundant array of inexpensive disks, now commonly redundant array of independent disks) is a data storage virtualization technology that combines multiple physical disk drive components into a single logical unit for the purposes of data redundancy, performance improvement, or both.

RAID (redundant array of independent disks; originally redundant array of inexpensive disks) provides a way of storing the same data in different places (thus, redundantly) on multiplehard disks (though not all RAID levels provide redundancy). By placing data on multiple disks, input/output (I/O) operations can overlap in a balanced way, improving performance. Since multiple disks increase the mean time between failures (MTBF), storing data redundantly also increases fault tolerance.

RAID arrays appear to the operating system (OS) as a single logical hard disk. RAID employs the technique of disk mirroring or disk striping.