PostgreSQL versions 8.2+ provide a simple, fast and stable replication mechanism, known as Warm Standby, though more accurately described as Log Shipping.
Data from the transaction log, also known as the Write Ahead Log (WAL) is transported to a standby server where continuous recovery takes place. It's a simple and elegant solution, relying on the underlying recovery code to perform changes on the standby node, so there is only minimal overhead on the primary server.
Data is currently shipped one file at a time, offering file based asynchronous replication. The entire database server is replicated, so there is no additional administration for each table or for each database. Replication can be fast in many circumstances and utilizes WAN links effectively.
As major developers and committers of the PostgreSQL project we are developing further updates to this replication mechanism, covering:
- Data streaming
- Synchronous Replication
- Read Only Standby Servers, also known as Hot Standby
- Increased replication performance
Postgres log shipping works using similar concepts to the following products options in other RDBMS (trademarks acknowledged appropriately):
- Oracle Data Guard
- IBM DB2 HADR
- Microsoft SQL Server Log Shipping
- Informix HDR (On-Bar)