C-JDBC is an open source Java middleware that provides fault tolerance and performance scalability to databases using clustering techniques at the JDBC level.

JDBC provides high availability transparent database clustering (partitioning, replication, etc.) to any Java application through JDBC. It works with any Java application without code modification and with any database engine. A performance evaluation using a servlet version of the TPC-W benchmark shows that scalable performance can be achieved using open-source databases and commodity hardware. It has been successfully tested with Tomcat, JBoss, JOnAS, WebSphere, MySQL, PostgreSQL, HSQL, SAP DB, Oracle, DB2, Sybase, MS SQL Server, Firebird, and more.

This technology it uses is great for the open source databases because it allows users to cluster them easily. It is freely available in the web.