Join the Shortest Queue (JSQ) is a popular routing policy for server farms. However, until now all analysis of JSQ has been limited to First-Come-First-Serve (FCFS) server farms, whereas it is known that web server farms are better modeled as Processor Sharing (PS) server farms. We provide the first approximate analysis of JSQ in the PS server farm model for general job size distributions, obtaining the distribution of queue length at each queue. To do this, we approximate the queue length of each queue in the server farm by a one-dimensional Markov chain, in a novel fashion. We also discover some interesting insensitivity properties for PS server farms with JSQ routing, and discuss the near-optimality of JSQ.
Using the exact analysis for the case of two servers, Gupta et al. REF obtained the first approximate analysis of the marginal equilibrium distribution of the queue lengths in a server farm with JSQ routing protocol, processor sharing service discipline and generally distributed service times.
Analysis of Join-the-Shortest-Queue Routing for Web Server Farms
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Computer Science