High availability refers to the practice of keeping online resources available through node failure or system maintenance. This guide will demonstrate a method for using two Linodes to provide HTTP load balancing services with nginx. Services will be avilable even when one load balancer node is powered off or put into standby mode. IP failover, Heartbeat 3.x, and Pacemaker 1.x will be used for this example configuration.
This setup is intended to provide a load balancer that distributes inbound HTTP requests to a pool of frontend web/application servers in the same datacenter. The web servers could host mirrored content locally on each of their filesystems, or they could mount content directories over NFS and access databases hosted on another highly available server cluster. A simple network diagram illustrating such a setup might look like this: