Disk Mirroring, What Is?
Disk mirroring is a method of backing up a disk in which anything that is written to a disk is simultaneously written to a another (second) disk. This creates fault tolerance in the critical storage systems. If a physical hardware failure occurs in a disk system, the data is not lost, as the other hard disk contains an exact copy of that data. Mirroring can be either hardware or software based. Hardware-based mirroring is implemented through the use of RAID controllers installed in the system to which separate hard disk drives are attached. These hard disks appear as different volumes to the system. Each data sector is identically written to all the volumes, thus creating multiple copies of the volumes. At the expense of mild system performance degradation, fault tolerance is introduced to the system. Software-based mirroring requires certain mirroring applications to be installed in the system. The software-based mirroring solution is usually less expensive and more flexible, b...