Before revision:  We derive the efficient redundancy level as a function of tasks' service time distribution . We observe that , the redundancy level that minimizes average  compute time is not necessarily the same as the redundancy level that maximized compute timepredictability .
After revision:  We derive the efficient redundancy level as a function of tasks' service time distribution at workers. We show that the redundancy level that minimizes average compute time is not necessarily the same as the redundancy level that maximized compute timepredictability .