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Conference Papers Year : 2017

Economies of scale in parallel-server systems

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We consider a parallel-server system with K homogeneous servers where incoming tasks, arriving at rate λ, are dispatched by n dispatchers. Servers are FCFS queues and dispatchers implement a size-based policy such that the servers are equally loaded. We compare the performance of a system with n> 1 dispatchers and of a system with a single dispatcher. Every dispatcher handles a fraction 1/n of the incoming traffic and balances the load to K/n servers. We show that the performance of a system with n dispatchers, K servers and arrival rate λ coincides with that of a system with one dispatcher, K/n servers and arrival rate λ/n. Therefore, the performance comparison can be interpreted as the economies of scale in a system with one dispatcher when we scale up the number of servers and the arrival rate proportionately. We consider two continuous service time distributions: uniform and Bounded Pareto that have increasing and decreasing failure rates, respectively; and a discrete distribution with two values, which is the distribution that maximizes the variance for a given mean. We show that the performance degradation is small for uniformly distributed job sizes, but that for Bounded Pareto and two points distributions it can be unbounded.

Dates and versions

hal-03109263 , version 1 (13-01-2021)



Josu Doncel, Samuli Aalto, Urtzi Ayesta. Economies of scale in parallel-server systems. IEEE Infocom, May 2017, Atlanta, United States. pp.1--9, ⟨10.1109/INFOCOM.2017.8057093⟩. ⟨hal-03109263⟩
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