Several years ago I was making a new web server environment to a big company. The company middle-director said that the environment must have 100% availability and online time. Itried to explain that there is no such thing in this world and even the servers in banks have a little downtime because of maintenance at least once a year. The client interrupted me and said: "but OUR servers MUST HAVE 100% online time!". Apathetically I responded: "As you wish..."