What would happen if a server hosting one or more applications was accidentally unplugged or shut down? Maybe there is a hardware failure or a server is hacked because it was not protected appropriately. These are just a few of the many scenarios that can bring a server down. Depending on what applications are hosted on a given server, situations like this can be devastating. So developers should always plan for the worst case, ideally going for a high availability (HA) infrastructure.
How bad is it really when a server goes down? If it is hosting an e-commerce web solution, there might be a few sales lost, but ...