Using Fault Model Enforcement to Improve Availability

Today’s network services run on complex arrays of computing systems consisting of a myriad of hardware and software components. In this work, we claim that it is impractical to try to tolerate all (or even a significant fraction of) fault types in these systems. We argue instead that a new approach, called fault model enforcement, that maps actual faults to expected faults of an abstract fault model can be used to increase system availability. This enforcement approach works because it transforms faults not factored into the initial design into faults that the system was designed to tolerate. Using fault injection and analytic modeling, we show that this enforcement approach has the potential to decrease the unavailability of a distributed Web server by over 50%.