Global Mirror is an IBM technology that provides data replication over extended distances between two sites for business continuity and disaster recovery. If adequate bandwidth exists, Global Mirror provides an recovery point objective (RPO) of as low as 3–5 seconds [1] between the two sites at extended distances with no performance impact on the application at the primary site. It replicates the data asynchronously and also forms a consistency group at a regular interval allowing a clean recovery of the application.
The two sites can be on separate continents or simply on different utility grids. IBM also provides a synchronous data replication called Metro Mirror, which is designed to support replication at "Metropolitan" distances of (normally) less than 300 km.[2]
Global Mirror is based on existing IBM Copy Services functions: Global Copy and FlashCopy. Global Mirror periodically invokes a point-in-time copy at the primary site, at regular intervals, without impacting the I/O to the source volumes. Then it transfers the copy to the recovery site. By grouping many volumes into one Global Mirror session multiple volumes may be copied to the recovery site simultaneously while maintaining point-in-time consistency across those volumes.
Global Mirror can be combined with a wide area clustering product like Geographically Dispersed Parallel Sysplex (GDPS), HACMP/XD, or CAW to provide for automated failover between sites. This combined solution provides lower recovery time objective (RTO), because it allows most applications to automatically resume productive operation in 30–600 seconds.
The Global Mirror function is available on IBM's enterprise storage devices including the DS8100, the DS8300, the DS6800, the Enterprise Storage Server Models 800 and 750, midrange storage servers DS4000 family and the IBM SAN Volume Controller.