Seeking Advice: postgreSQL Major Version upgrade for pgpool-II and streaming replication setup

Deal All,

We are planning a major PostgreSQL version upgrade. We have the following
setup:

- *Data Volume:* Terabytes of data, including Large Object (LOB) data.
- *Replication:* Streaming replication setup.
- *Load Balancing:* pgpool-II is used for load balancing and read/write
splitting.
- *Infrastructure:* All components are running on Virtual Machines (VMs).

We would greatly appreciate your guidance on the following aspects:

1. *Upgrade Procedure:*
- Should we start with stopping pgpool-II first, followed by the
standby server?
- Is it necessary to stop or delete anything on the standby server
related to replication before upgrading the primary?
- Then Should we delete the replication slot on the primary server
using pg_drop_replication_slot() before stopping the primary server? Is
there any other point we need to take care of before installing the new
postgres version on the primary and doing the upgrade using pg_upgrade
2. *Data Migration:*
- Given the large data volume, is it likely that streaming
replication will fail during the upgrade?
- Should we consider manually copying the data directory from the
upgraded primary server to the standby server as a more
efficient approach?
- If so, what are the best practices for copying the data directory?
3. *Post-Upgrade Steps:*
- After the primary server upgradation, new version installation on
standby, data copy from primary to standby should we then create the
replication slot on primary and setup the streaming replication the same
way as was done earlier - creating standby file, updating conninfo and
starting replication using pg_basebackup?

We are eager to learn from your expertise and ensure a smooth and
successful upgrade process.

Thank you for your time and valuable insights.

Sincerely,

Ramzy