A big benefit of cloud computing is the ease with which you can add resources to meet increasing demand. Same goes for reduced demand. This is known as elasticity.
Windows Azure makes this a snap via its config files. Sometimes you may wish to eliminate the manual effort altogether and design a solution that automatically scales based on performance and load.
This is possible via Azure’s REST based management API. Joseph Fultz explains this approach in the October 2010 MSDN article, Performance-Based Scaling in Windows Azure: http://msdn.microsoft.com/en-us/magazine/gg232759.aspx