Redundant Array of Independent Disks better known as RAID , a technique to use multiple disks in concert to build a faster, bigger, and more reliable disk system.The term was introduced in the late 1980s by a group of researchers at U.C. Berkeley (led by Professors David Patterson and Randy Katz and then student Garth Gibson).
RAIDs offer a number of advantages over a single disk. One advantage is performance. Using multiple disks in parallel can greatly speed up I/O times. Another benefit is capacity. Large data sets demand large disks. Finally, RAIDs can improve reliability; spreading data across multiple disks (without RAID techniques) makes the data vulnerable to the loss of a single disk; with some form of redundancy, RAIDs can tolerate the loss of a disk and keep operating as if nothing were wrong.