PowerHA SystemMirror linked cluster

A linked cluster is ideal for situations where each site is at a different geographical location. Typically, the sites are far enough apart so that they cannot conveniently share a common storage area network (SAN). Each site must have its own active repository disk, and any backup repositories. Linked clusters always use unicast to communicate between sites. Linked clusters are a useful part of high availability disaster recovery (HADR).

Cluster Aware AIX® (CAA) can use linked clusters to support multiple sites that are geographically far apart (in different cities). Linked clusters link the individual CAA clusters to the sites that are at different locations. The links between the sites are used for heartbeat and cluster communication.

You can use linked clusters for communication across short geographical distances, such as between different buildings within the same city.

The following table displays the supported linked cluster configurations for split policy options and merge policy options. For example, in a linked cluster you can have a configuration with a split policy value of None and a merge policy value of either Majority or Priority. However, you cannot have a configuration with a split policy value of Tie-breaker and a merge policy value of Manual.
Table 1. Linked cluster options for split and merge policies
Split policy options Merge policy options
Majority Priority Tie-breaker Manual
None X X    
Tie-breaker     X  
Manual       X
The following figure displays a linked cluster where the sites are at different cities and each site has its own repository disk.
Figure 1. Typical linked cluster configuration
Displays site 1 in New York City, New York and site 2 in Los Angeles, California. Each site has its own repository disk.