Comments - Configuring MariaDB Replication between Two MariaDB Galera Clusters

It might be a good idea to add that circular replication in this configuration might not be safe with simultaneous updates to both clusters due to the possibility of independent key clashes, esp when replication delay and wsrep_cert_deps_distance are non-zero.

To have both clusters simultaneously active, it is a good idea to turn off wsrep_auto_increment_control and manually assign a unique autoincrement key value to each node in the complete architecture.

For example, if you have a production cluster P with three nodes, and a recovery cluster R with three nodes, setting the following values would work:

auto_increment_increment=10
auto_increment_offset=1 ## Values here would be unique, so P1=1, P2=2, P3=3, R1=6, R2=7, R3=8
wsrep_auto_increment_control=0