I am using pgpool with streaming replication option for PostgreSQL, with a failover command (shell script). 2 pgpool instances (with watchdog) on the database nodes. You were referring to split brain for pgpool instances or PostgreSQL instances?
I was talking about split-brain for pgpool which cascades to respective PostgreSQL instances i.e. pgpool would think that the other node is lost and hence it assume itself as only available pgpool+DB node and hence pgpool on slave will switchover to its on DB and pgpool on master will consider slave to be lost. This can happen if there is a network fluctuation between slave and master (can be avoided with redundant network path/line between two servers).
I do not understand if you are using HA mode, how come you are not using Virtual IP (you mentioned earlier).
Just curious - once pgpool switches to the slave, it will mark it as primary (I did not use virtual IPs.) So spli-brain scenarion will not happen,right?
Am I missing something here? or some mode of pgpool which I am not aware of?