MySQL Split Read/Write for Drupal is a patch for Drupal versions 5 and 6 that allows a Drupal-based Web site to access a multi-server MySQL setup with master/slave replication. This allows Drupal to send all MySQL select (read) queries to the slave nodes, while allowing insert, update, and select (write and read) queries to be pointed at the master node. The code modification allows for an increased 30% improvement under query-based transactions on this platform environment.
Galera wsrep provider is a dlopenable generic replication library which implements the wsrep provider API. It provides very efficient synchronous replication, and multi-master and "parallel applying" capabilities for opaque data buffers. Its primary focus is data consistency. A transaction is either committed on every node, or not at all. It works anywhere TCP works, including on WAN, and can utilize UDP multicast where available. It is used by the MySQL-wsrep patch project to create true multi-master MySQL/InnoDB clusters.