What does the term "disk mirroring" refer to in the context of RAID?

Disk mirroring in the context of RAID refers to the process of duplicating data across multiple drives. This technique ensures that an exact copy of the data exists on at least two drives simultaneously. If one drive fails, the system can seamlessly continue to operate using the other drive that holds the mirrored data. This method enhances data redundancy and reliability, making it a key feature in RAID configurations, particularly in RAID 1, where data is mirrored for protection against disk failure.

The other options do not accurately describe disk mirroring. Writing data to a single disk does not provide the redundancy that mirroring offers. Striping involves dividing data into blocks and spreading it across multiple drives, focusing on performance rather than redundancy, and creating a backup of data on external storage is a different process that typically involves copying data to a separate location rather than real-time duplication within a RAID array. Each of these alternatives serves different purposes and does not reflect the principle of disk mirroring.