20 years ago ?
"Capacity planning is an old science - in IT terms, at least. Over 20 years ago, DP managers were analyzing the trends in their resource usage, mainly so they could predict when they would need to buy more processing power or storage." - Yes, it is an old science but I'm sorry, being in this business 35+ years. We did capacity planning, not just hardware or whatever, but everything in 70's. It is an art and for a long time forgotten, unfortunately. It always starts from from system / application design, a bad system can eat any installation no mater how much hardware there is. Amazing how the old fallacies live. Seen that too many times and the excuses, sad! And no tool can help you if the requirements are not very well defined up front.