GLB is a user-space TCP load balancer similar to Pen. It lacks most advanced Pen features, as the aim was to make a user-space TCP proxy that is as fast as possible. It can utilize multiple CPU cores. A list of destinations can be adjusted in runtime. Destination "draining" is supported. It supports "least connected", "round-robin", "random", and "source tracking" balancing policies.
wsrep-enabled MySQL (previously MySQL/Galera cluster) can use wsrep replication providers, such as Galera, to form a cluster. wsrep API is an abstract replication interface that supports global transaction ID, true multi-master capability, conflict detection and resolution, and parallel applying and is transparent to triggers, stored procedures, and functions by replicating only final transaction results. Only the InnoDB storage engine and DDL commands are supported by this patch.
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.