RAID stands for redundant array of independent disks or redundant array of inexpensive disks.
A redundant array of independent disks is a technique that consists of storing the same data in different locations on several hard disks, in order to increase their accessibility and security.
Data is distributed across disks in a different way, called a RAID level, depending on the level of redundancy and performance required. The different schemes, or data distribution arrangements, are referred to as “RAID” followed by a number, for example RAID 0 or RAID 1. Each scheme, or RAID level, offers a different balance of key objectives: reliability, availability, performance and capacity. RAID levels higher than RAID 0 offer protection against unrecoverable sector read errors, as well as against whole physical disk failures.