Redundant Arrays of Independent Disks (RAID)
| 1. Redundant Arrays of Independent Disks or RAID is a group of disks that is configured to appear as a single disk drive to the host.
Notes (1): These independent disks or RAID uses many smaller disks instead of using one large disk to store data, because this is a less expensive approach to using many low-cost drives as a group to improve performance, yet also provides a degree of redundancy that makes the chance of data loss remote.
2. A way of storing the same data over multiple physical disks to ensure that if a hard disk fails a redundant copy of the data can be accessed instead. Example schemes include mirroring and RAID–5.
(Source: Microsoft Storage Glossary)