<A target="_blank" href="http://blog.nashcom.de/nashcomblog.nsf/dx/configuring-sai-loadmon-for-fast-servers.htm">Daniel Nashed says the Server Availability Index</A> (SAI) may not always report correct information. It seems, if your server is really, really fast, the formula used to calculate availability can be thrown off. A new approach is available under Domino 8.5.