The Metro Mirror Copy Service provides a synchronous copy, which means that the primary virtual disk (VDisk) is always an exact match of the secondary VDisk.
The host application writes data to the primary VDisk but does not receive confirmation that the write operation is complete until the data is written to the secondary VDisk. For disaster recovery, this mode provides the simplest mode of operation because a synchronous copy of the data is maintained. Metro Mirror is constrained by the latency time and bandwidth limitations that are imposed by the communication link to the secondary site.