Global Mirror

Start of change Global Mirror uses the same base technology as Metro Mirror except the transmission of data is done in an asynchronous manner. Global Mirror on the DS8000® and with SAN Volume Controller and Storwize® system change volumes requires a third set of disks to maintain data consistency. End of change

Start of change Because this data transmission is asynchronous, there is no limit to how geographically dispersed the System Storage® servers can be from each other. End of change

Characteristics of Global Mirror

IBM® System Storage Server solution that is integrated with PowerHA® cluster framework.
Second copy of data can be geographically dispersed over potentially large distances.
Two System Storage Servers are required.
Two copies of the data on the target System Storage Server are required to ensure consistency of data across distances.
Offline saves and queries possible from a point in time copy of the data, maintaining data resiliency.
Data transmission is an asynchronous process. In flight data loss is possible.
Asynchronous data replication process does not affect application performance.
Replication of the independent disk pool data is at the disk sector level between the disks on the two Storage Servers. All objects in the independent disk pool will be synchronized.
Cost is associated with a second and third set of disk.
No system overhead to run Global Mirror, it is handled by the storage server.
Journaling the objects in the independent disk pool ensures that those changes are forced quickly to disk where they are then replicated to the target system.
Multiple Fibre Channel communication lines available for redundancy and increased bandwidth.