PostgreSQL Disaster Recovery#

A DR plan for PostgreSQL has three layers: streaming replication for fast failover, WAL archiving for point-in-time recovery, and a backup tool like pgBackRest for managing retention. Each layer covers a different failure mode – replication for server crashes, WAL archiving for data corruption that replicates, full backups for when everything goes wrong.

Streaming Replication for DR#

Synchronous vs Asynchronous – The Core Tradeoff#

Asynchronous replication is the default. The primary streams WAL to the standby, but does not wait for confirmation before committing. This means the primary is fast, but the standby can be seconds behind. If the primary dies, those uncommitted-on-standby transactions are lost.

Stateful Workload Disaster Recovery#

Stateless workloads are easy to recover – redeploy from Git and they are running. Stateful workloads carry data that cannot be regenerated. Databases, message queues, object stores, and anything with a PersistentVolume needs a deliberate DR strategy that goes beyond “we have Velero.”

The fundamental challenge: you must capture data at a point in time where the application state is consistent, replicate that data to a recovery site, and restore it in the correct order. Get any of these wrong and you recover corrupted data or a broken dependency chain.

PostgreSQL Backup and Recovery#

A backup you have never tested restoring is not a backup. This covers the main backup tools, when to use each, point-in-time recovery, and automation.

Logical Backups: pg_dump and pg_dumpall#

pg_dump exports a single database as SQL or a compressed binary format. It takes a consistent snapshot without blocking writes.

# Custom format (compressed, supports parallel restore)
pg_dump -U postgres -Fc -d myapp -f myapp.dump

# Directory format (parallel dump)
pg_dump -U postgres -Fd -j 4 -d myapp -f myapp_dir/

pg_dumpall exports every database plus cluster-wide objects. In practice, dump roles separately and per-database for flexibility:

PostgreSQL Replication#

Streaming replication gives you a full binary copy for high availability and read scaling. Logical replication gives you selective table-level syncing between databases that can run different PostgreSQL versions.

Streaming Replication Setup#

Configure the Primary#

# postgresql.conf
wal_level = replica
max_wal_senders = 5
wal_keep_size = 1GB

Create a replication role and allow connections:

CREATE ROLE replicator WITH REPLICATION LOGIN PASSWORD 'repl-secret';

# pg_hba.conf
host  replication  replicator  10.0.0.0/8  scram-sha-256

Initialize the Standby#

sudo systemctl stop postgresql-16
sudo rm -rf /var/lib/postgresql/16/main/*
pg_basebackup -h primary-host -U replicator -D /var/lib/postgresql/16/main \
  --checkpoint=fast --wal-method=stream -R -P
sudo chown -R postgres:postgres /var/lib/postgresql/16/main
sudo systemctl start postgresql-16

The -R flag creates standby.signal and writes connection info to postgresql.auto.conf. The standby now continuously receives and replays WAL from the primary, accepting read-only queries by default.