High Availability Failover is the ability for client connections to migrate from one server to another in event of server failure so client applications can continue to operate.
We currently have CSP application that runs under 2 servers(usually primary), and every month the server reboots for patching SERVER1(primary) in the morning and SERVER2(backup) at night.
Whenever the SERVER1 reboots SERVER2 behaves as primary and when SERVER1 comes back up it will act as backup server.
First Patching:
So, when SERVER1 is down, I need to start httpd service for SERVER2 and stop httpd service for SERVER1 (which is now backup server).