If China fails, then Beijing and Shanghai can
no longer replicate with other servers in the replication system; Guangzhou and Chengdu can replicate only with each other.
However, if China was part of a high-availability cluster,
when it failed, the secondary server would replace it and replication would
continue, as illustrated in Hierarchical Tree Topology with HDR. Figure 1: Hierarchical Tree Topology with HDR
In this example, Asia and Guangzhou, which are also
parent servers, might also benefit from using a high-availability
cluster to ensure high availability.