RAID is a set of technologies that are used to make more efficient use of disk resources.
It was originally designed back when disks were extremely expensive, not that large, and a major pain to back up. Also, backing them up was very labor intensive. With the addition of the ability to use multiple drive controllers, RAID quickly became the technology of choice for large, mission-critical database applications. 1 combines striping and mirroring. RAID-4 implements block striping with a dedicated parity disk.