You don't need a SQL dump to backup a PostgreSQL database. It has a mechanism (pg_start_backup) where it will only write WAL (journal) files and will not remove

You don't need a SQL dump to backup a PostgreSQL database. It has a mechanism (pg_start_backup) where it will only write WAL (journal) files and will not remove them while you use your filesystem backup (eg. rsync) as usual until you signal completion (pg_stop_backup), after which you also need to back up your WAL archive. This gives you everything you need to recover to any point between the start and stop of the backup operation, and it's guaranteed to be consistent assuming the data itself was copied successfully. This is because any inconsistent files modified during the copy will be recovered from the archived WAL files to attain a consistent state.