Making use of asynchronous replication

While point-in-time recovery is nice, it might not be enough. In many cases, people want an up-to-date standby server that can also serve as a read-only slave. A feature called streaming replication is exactly what is needed in this case.

Setting up streaming replication is easy and can be performed in a handful of steps:

1. Adapt postgresql.conf on the master server.

2. Change pg_hba.conf to allow remote base backups.

3. Run pg_basebackup to get an initial copy.

4. Fire up the slave.

To set up postgresql.conf, the following settings are needed:

wal_level = hot_standby
max_wal_senders = 5
hot_standby = on

The first two settings are mandatory on the master. The wal_level field tells the server to create enough xlog to allow streaming replication, and max_wal_senders will indicate the number of streams the master is allowed to keep open.

Tip

If you are planning to run one slave, consider setting max_wal_senders to 3 or higher. During streaming, only one wal-sender process...