Linux Load Averages: Solving the Mystery
What we need is a systems model that allows us to assess the overall health of a server in a single metric.  Indicators of something under strain will reflect itself in the metric and draw our attention for further drilldown and analysis.  "Load Average" is the metric we (the systems community) have generally been using for this.  Unfortunately it appears that the model it is based on may be rather dated and may have flaws which mean we will miss, or misinterpret system health status by relying on that number.  So the million dollar question is - starting from scratch, how can we design a model of our system that yields an reliable system health indicator metric?