Feedback control is a powerful technique for managing complex systems. Most people are familiar with examples of feedback control, even if they don't have a clear understanding of the underlying theory. For example, anti-lock brakes use feedback control to ensure that a driver can quickly stop the car without skidding and losing control. Sensors attached to each wheel send measurements to a controller that adjusts the amount of braking force applied to each wheel. If too much force is applied to a wheel and it starts to skid, then the sensor detects that the wheel is locking. The controller reduces brake force, reapplying it when it detects that the wheel is turning again.
In the data center, many tools are available to deploy configuration changes. What is often missing are the sensors to provide the data center wide visibility needed to determine where configuration changes (controls) should be applied and to assess the effectiveness of the changes. The sFlow sensors, built into network devices from most network vendors, in combination with an sFlow analyzer, provide the feedback that is essential to maintain effective control over the data center.