PG Upgrade with hardlinks, when to start/stop master and replicas

Hello everyone!

We are about to upgrade a 6 instance cluster from pg92 to pg10 using pg_upgrade with hardlinks and rsync.

Our preliminary tests are working really good so far but on question has popped up that we feel is really critical because it has an important impact on our failover plan.

After reading the pg_upgrade documentation multiple times, it seems that after running pg_upgrade on the primary instance, we can't start it until we run rsync from the primary to the standby. I'm understanding this from the following section in the pg_upgrade manual page.


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I'm understanding the `any` as primary and standbys.

On the other hand, we've been doing tests that start the primary instance as soon as pg_upgrade is done. This tests have worked perfectly fine so far. We make the rsync call with the primary instance running and the standby can start later on after rsync is done and we copy the new configuration files.

If what we are doing is wrong, we need to run `rsync` before starting the primary instance, that would mean that the primary and the standby are not usable if pg10 doesn't start correctly in the primary right ? 

I hope my question is clear enough! 

Best,