PostgreSQL 12 High Availability Cookbook - Third Edition

Getting ready

Since we're working with DRBD and need a fully established mirror, please follow the steps in all of the recipes up to Adding block-level replication before continuing. In addition to this, we need to simulate a split brain. A very easy way to do this is to put both nodes in the primary state while disconnected from each other.

Assuming that we have nodes pg1 and pg2, where pg1 is the current primary node, follow these instructions as the root user to cause a split brain:

1. On both nodes, disconnect from DRBD with this command:

drbdadm disconnect pg

2. On pg2, execute this command to force it into primary status:

drbdadm primary --force pg

If we were to use drbdadm to attempt to connect the nodes now, we would see the following ...