“Two-Stagification”: Job Dispatching in Large-Scale Clusters via a Two-Stage Architecture

A continuing effort is devoted to devising effective dispatching policies for clusters of First Come First Served servers. Although the optimal solution for dispatchers aware of both job size and server state remains elusive, lower bounds and strong heuristics are known. In this paper, we introduce a two-stage cluster architecture that applies classical Round Robin, Join Idle Queue, and Least Work Left dispatching schemes, coupled with an optimized service-time threshold to separate large jobs from shorter ones. Using both synthetic (Weibull) workloads and real Google data center traces, we demonstrate that our two-stage approach greatly improves upon the corresponding single-stage policies and closely approaches the performance of advanced sizeand state-aware methods. Our results highlight that careful architectural design—rather than increased complexity at the dispatcher—can yield significantly better mean response times in large-scale computing environments.