On the Accuracy of Trace Replay Methods for File System Evaluation

Abstract

Current trace replay methods for file system evaluation fail to represent traced workloads accurately. When using a misrepresented workload one may take wrong conclusions about the system evaluation. For example, a system designer can miss performance problems if the replay of a trace produces an under loaded representation of the real workload. Even worse, one can take wrong design decisions, leading to optimization of untypical workloads. In this study, we captured and replayed traces from standard file systems using methods proposed in the literature, to exemplify the inaccuracy of state-of-art trace replay methods. We also exposed a shortcoming of current methodologies, in a replay of a general purpose workload trace, we observed a difference of up to 100% on request response time, caused by the choice of trace replay method.