In Conclusion

Preventing the possibility of a split-brain condition while eliminating single points of failure in a high-availability server configuration is tricky. The goal of your high-availability server configuration should be to accomplish this with the least amount of complexity required. When you finish building your high-availability server pair you should test it thoroughly and not feel satisfied that you are ready to put it into production until you know how it will behave when something goes wrong (or to use the terminology sometimes used in the high-availability field: test your configuration for its ability to properly handle a fault, and make sure you have good fault isolation).

This ends Part II. I have spent the last several chapters describing how to offer client computers access to a service or daemon on a single IP address without relying on a single server. This capability—the ability to move a resource from one server to another—is an important building block of the high-availability cluster configuration that will be the subject of Part III.