http://db-engines.com/en/system/MariaDB%3BMySQL%3BPercona+Server

http://galeracluster.com/products/

Galera Cluster for MySQL is a true Multimaster Cluster based on synchronous replication. Galera Cluster is an easy-to-use, high-availability solution, which provides high system uptime, no data loss and scalability for future growth.

https://www.percona.com/software/mysql-database/percona-xtradb-cluster

It integrates Percona Server and Percona XtraBackup with the Codership Galera library of MySQL high availability solutions in a single package that enables you to create a cost-effective MySQL high availability cluster.

https://mariadb.com/kb/en/mariadb/what-is-mariadb-galera-cluster/

MariaDB Galera Cluster is a synchronous multi-master cluster for MariaDB.

クラスタの仕組み（処理？）を作ったのがGALERAで、Percona＋GALERA＝XtraDB Cluseter、MariaDB＋GALERA＝Galera Cluster。