A fault-tolerant technique that writes the same information simultaneously onto two hard disks or two hard-disk partitions, using the same disk controller. If one disk or partition fails, information from the other can be used to continue operations. Disk mirroring is offered by most major network operating systems. It is designed to protect the system against a single disk failure, not multiple disk failures. Disk mirroring is no substitute for a well-planned series of disk backups.
See also data protection; disk duplexing; redundant array of inexpensive disks.