Here are a few differences between basebackup and rsync.
pg_basebackup is easier, as it's a single command with PostgreSQL support. Data consistency is automatically ensured by postgresql. It transfers the entire database, potentially high network bandwidth is required. It is less flexible, due to mostly predefined options.
rsync is more complex, it requires multiple manual steps. This method requires stopping or ensuring the primary server's data directory is in a consistent state before starting the synchronization, Which can cause downtime or performance impact. It requires careful handling to ensure data consistency. It is more efficient with bandwidth, as it only transfers changes. It is more flexible with control over what gets copied.
You can use basebackup if you want a straightforward, reliable way to create a base backup. If you are looking for a method that integrates directly with PostgreSQL's replication capabilities. Network bandwidth and performance impact on the primary server are not critical concerns. If you want an automated process that requires less manual intervention.
You can use rsync if you have specific requirements for how the data should be copied (e.g., selective file copying). If you need more control over the synchronization process or want to optimize for minimal network usage. If you have a large dataset and want to minimize the data transfer by only copying changes after an initial sync. If you are comfortable with handling data consistency and can manage the additional complexity.
