Using Fault Injection to Evaluate the Performability of Cluster-Based Services

We propose a two-phase methodology for quantifying the performability (performance + availability) of cluster-based Internet services. In the first phase, evaluators use a fault-injection infrastructure to measure the impact of faults on the server’s performance. In the second phase, evaluators use an analytical model to combine an expected fault load with measurements from the first phase to assess the server’s performability. Using this model, evaluators can study the server’s sensitivity to different design decisions, fault rates, and other environmental factors. To demonstrate our methodology, we study the performability of 4 versions of the PRESS Web server against 5 classes of faults. We use Mendosus, a new fault-injection and network emulation infrastructure, to effect phase 1 of our methodology. We then use our model to quantify the performability of the different versions of PRESS. We also use the model to study the impact of reducing live operator support and adding RAIDs on PRESS’s performability.