Every HA architecture has common problems to solve or common questions to respond to:
How the connection can be handled
How the failover can be managed
How the storage is shared or replicated to other sites
There are some production-stable and widely used solutions for each one of those questions. Let's study these questions in detail:
How the connection can be handled
One of the possible answers to this question is just one word—VIP (Virtual IP). Basically, every software component needs to communicate or is interconnected with different logical layers, and those components are often deployed on different servers to divide and equalize the workload. Much of the communication is TCP/IP-based, and here the network protocol gives us a hand.
It is possible to define a VIP that is assigned to the active servers and all the software required to be configured to use that address. So if there is a failover, the IP address will follow the service and all the...