Questions on Upgrading PostgreSQL from 15.0 to 15.9 and Setting Up Streaming Replication

[Subhash Udata <subhashudata@xxxxxxxxx>]

Dear PostgreSQL Community,

I have a production database setup with a primary server and a standby server. The database is currently running on PostgreSQL 15.0, and I plan to upgrade both servers to 15.9.

I have the following questions regarding the upgrade and replication process:

1. Upgrade and Replication Compatibility:

   • My plan is to perform a failover, promote the standby server (currently 15.0) to primary, and then upgrade the old primary server to version 15.9.
   • After upgrading the old primary server to version 15.9, I want to configure it as a standby server and set up streaming replication with the new primary server, which will still be running version 15.0.
   • Is it possible to establish streaming replication between these two versions (15.0 as primary and 15.9 as standby)?

2. Efficient Replication Setup:

   • The production database is around 1TB in size, and creating replication using pg_basebackup is taking more than 2–3 hours to complete.
   • Is there an alternative method to set up replication without taking a full backup of the entire cluster but instead using only the WAL files that have changed on both servers?

Your guidance and recommendations on these questions will be greatly appreciated.

Thank you for your time and support!

Best regards,

Subhash