Here are a couple of basic statements regarding Demand for services and available capacity:

1. Unused capacity is permitted if it provides higher level of assurance (i.e. conscious idle capacity)
2. Insufficient capacity limits service growth and impacts performance

While these may seen like basic statements it is surprising the number of times an IT professional wants to build an infrastructure that has an excess in idle capacity. This is mistakenly thought of by the IT profession as good planning. However, it is actually the result of POOR or NO PLANNING; a total lack of understanding about demand and evidence of poor service provider to business communication.

The reality is that consumption must drive the demand or production of services. Otherwise we would have a “glut” of capacity which will ultimately be used for a purpose that it wasn’t intended for. I have created a LAW to explain:

PURDIE’S LAW of DIMINISHING DATA STORAGE and OTHER FINITE RESOURCES which states that:

Irrespective of how much of a resource you make available for a given purpose any excess will be used  for reasons other than that for which is was intended.

I use data storage as my main focal point as there are thousands of stories that involve the purchase of more than twice the disk space required for any initial demand. However, the disk space/resource  then gets used for other purposes and when ultimately required for the initial project it has been mysteriously used.

This is the reality that most IT professionals have some experience with. Whether it is data storage, CPU cycles on a microprocessor, or network bandwidth; then no matter how much spare capacity was bought to cater for “unforeseen” spikes or gradual increases in demand for purpose X; over time that spare capacity gets used for everything other than purpose X.

This ultimately leads to rushed purchasing decisions, conflict and dispute and generally adds to the credibility woes of an IT Service Provider.