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Surprising Results on Task Assignment in Server Farms with High-Variability Workloads
| Citations: | 14 - 3 self |
BibTeX
@MISC{Harchol-balter_surprisingresults,
author = {Mor Harchol-balter and Alan Scheller-wolf and Andrew Young},
title = {Surprising Results on Task Assignment in Server Farms with High-Variability Workloads},
year = {}
}
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Abstract
This paper investigates the performance of task assignment policies for server farms, as the variability of job sizes (service demands) approaches infinity. Our results reveal that some common wisdoms regarding task assignment are flawed. The Size-Interval-Task-Assignment policy (SITA), which assigns each server a unique size range, was heretofore thought of by some as the panacea for dealing with high-variability job-size distributions. We show SITA to be inferior to the much simpler greedy policy, Least-Work-Left (LWL), for certain common job-size distributions, including many modal, hyperexponential, and Pareto distributions. We also define regimes where SITA’s performance is superior, and prove simple closed-form bounds on its performance for the abovementioned distributions.
Keyphrases
task assignment server farm surprising result high-variability workload service demand job size common wisdom pareto distribution simpler greedy policy many modal simple closed-form bound unique size range abovementioned distribution sita performance certain common job-size distribution task assignment policy size-interval-task-assignment policy high-variability job-size distribution
