pgcluster 介绍

- Since a replication system is a synchronous replication, delay does not occur with the data duplicate between the Cluster DBs.
　　系统属于同步复制，cluster DBs间不会发生延时。
- Since a server is multi-master composition, two or more the Cluster DBs can receive access from a user simultaneously. 
　　多主机架构，cluster DBs能够同时处理用户请求。

- The session load of a reference request is distributed. It is effective at the Web application with which a reference request pours in.
- A replication object can be specified per table. When the tables which receive an updating request and a reference request differ, the PGCluster can distribute the table which receives an updating request and can reproduce only the table which receives a reference request. 

- When failure occurs in Cluster DB, a load balancer and a replication server separate Failure DB from a system, and continue service using the remaining DB. Since separation of Failure DB and continuation of service are performed simultaneously, most service stop time is made to 0.
- The Cluster DB which repair finished can be dynamically restored to a system, without stopping service.
- Data is automatically copied to DB restored or added from other DB. The query which received during restoration is executed from the replication server after restoration.