Metro Mirror, which is performed at the volume level, provides a continuous, synchronous mirror of a set of data to a different storage system up to 300 km (188 miles) away. Because the mirror is updated in real time, no data is lost when a failure occurs. Metro Mirror is generally used for disaster-recovery purposes, data protection and data vaulting. It's also used to migrate data from a primary to a secondary system, while the primary system remains active. Metro Mirror can be implemented when both the source and target are on the same storage area network (SAN) or when they are on separate, remote SANs without having to use channel extenders.
