Answer Description
Redundant Array of Independent Disks 1 (RAID) uses disk mirroring to ensure every piece of data can also be found on another hard drive. This means if a single disk fails, another disk will still have the necessary data.
Wikipedia
RAID (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.
Data is distributed across the drives in one of several ways, referred to as RAID levels, depending on the required level of redundancy and performance. The different schemes, or data distribution layouts, are named by the word RAID followed by a number, …
RAID - Wikipedia, the free encyclopedia