Initially I have two database server (Master Master Replication config with Haproxy load balancing) A and B. And two application server say P and Q. Both P and Q is pointed towards A will move to B in case of failure. OLTP operations are huge in numbers per minute.
Now we are adding two more app servers R and S.
Just want to know experts opinion. Is it ok to point both R and S towards A? Or should I use B this time.