pgpool-II allows multiple PostgreSQL servers (DB nodes) to be connected, which enables queries to be executed simultaneously on all servers. It enables "parallel query" processing. Also, pgpool-II can be started as pgpool-I by changing configuration parameters. pgpool-II that is executed in pgpool-I mode enables multiple DB nodes to be connected, which was not possible in pgpool-I. WWW: http://pgpool.projects.postgresql.org/pgpool-II/en/