MariaDB master-master and master-slave replication at the same time

Question

Currently I have 2 data centers and mariaDB master-master semi-sync replication will be employed to synchronize data between 2 sites.

In order to improve local availability, we are planned to deploy one more mariaDB in each site to form a master-slave replication. ie Cross-site replication is master-master replication, while local replication is master-slave replication

I would like to know if this topology makes sense and technically feasible to do.

Can mariaDB support mixed-mode of replication at the same time?

Answer 1

No you can't have partial asynchronous master slave and semi-sync on the same server.

I recommend moving to either Galera (3 sites recommended to alleviate split brain or devise an alternative resolution);

Or multi-master all-(server)-to-all-(other-servers) replication (without log-slave-updates).

Answer 2

A Master can have any number of Slaves; those slaves can be either local to the Master's datacenter, or remote. One of those "Slaves" can be another Master, thereby giving you "dual-Maser".

For Dual-Master, I recommend writing to only one of them (until a failover).

These are partial HA solutions: * Replication * Dual-Master * Semi-sync * Using only 2 datacenters

Galera (and soon, Group Replication) are better than any combination of the above. But for good HA, you need 3 geographically separate datacenters (think flood, tornados, etc)

I am not familiar with a restriction against async + semi-sync on the same server.

Be aware that every Slave must perform every write operation, so a Slave is not necessarily less busy than a Master. However, having more than one server for "reads" does spread out the read load.

For Galera, 3 nodes is recommended. 4 or 5 is OK; more than 5 may stress the network and the handshaking needed. Galera allows any number of Slaves hanging off each 'node'.