The Watt Governor and its relevance to software systems
The Watt Governor and itsrelevance to software systemsMatthew Skeltoncontact@matthewskelton.net
2Watt Governor• What is the Watt Governor?• How it works• Control systems• Why it is important• Applications• Relevance to computer systems• Q&A
3What is the Watt Governor?• Mechanical device used in steam engines to regulate speed• 1st-order negative feedback device• Invented around 1788 by James Watt (Scotland)• Etymology: ▫ “Governor/Government” and “Cybernetics” both share a common Greek root: κσβερνός (steersman)
4How it works• Connected to machine drive mechanism• As speed increases, weights are thrown further outwards• Opens/closes a throttle valve to control input• Goal: steady speed, independent of load
6Why this is important• Recall: steady speed, independent of load• Result: predictable output• Allows planning of: ▫ Capacity ▫ Cost ▫ Delivery• Better service from the system
7Applications• Not just mechanical devices• Concept can be applied to other self-regulating systems ▫ Human societies, including organisations ▫ Planetary weather ▫ Evolution of species• Absence of governance leads to “run-away” speeds (and melt-down)
8Relevance to Computer Systems• Physical application: ▫ Hardware power and cooling• Computer software: ▫ Resource Governor – SQL Server 2008• Service Management• Cloud Computing ▫ Potential for much greater and more dynamic scalability than before• Problems have been solved before... since 1788!