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Diffusion approximations for load balancing mechanisms in cloud storage systems

Published online by Cambridge University Press:  22 July 2019

Amarjit Budhiraja*
Affiliation:
University of North Carolina at Chapel Hill
Eric Friedlander*
Affiliation:
University of North Carolina at Chapel Hill
*
*Postal address: Department of Statistics and Operations Research, University of North Carolina at Chapel Hill, NC 27599, USA.
*Postal address: Department of Statistics and Operations Research, University of North Carolina at Chapel Hill, NC 27599, USA.

Abstract

In large storage systems, files are often coded across several servers to improve reliability and retrieval speed. We study load balancing under the batch sampling routeing scheme for a network of n servers storing a set of files using the maximum distance separable (MDS) code (cf. Li (2016)). Specifically, each file is stored in equally sized pieces across L servers such that any k pieces can reconstruct the original file. When a request for a file is received, the dispatcher routes the job into the k-shortest queues among the L for which the corresponding server contains a piece of the file being requested. We establish a law of large numbers and a central limit theorem as the system becomes large (i.e. n → ∞), for the setting where all interarrival and service times are exponentially distributed. For the central limit theorem, the limit process take values in 2, the space of square summable sequences. Due to the large size of such systems, a direct analysis of the n-server system is frequently intractable. The law of large numbers and diffusion approximations established in this work provide practical tools with which to perform such analysis. The power-of-d routeing scheme, also known as the supermarket model, is a special case of the model considered here.

Type
Original Article
Copyright
© Applied Probability Trust 2019 

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