Mean-field analysis of coding versus replication in large data storage systems

L. I. Bin, Aditya Ramamoorthy, R. Srikant

Research output: Contribution to journalArticle

Abstract

We study cloud storage systems with a very large number of files stored in a very large number of servers. In such systems, files are either replicated or coded to ensure reliability, i.e., to guarantee file recovery from server failures. This redundancy in storage can further be exploited to improve system performance (mean file-access delay) through appropriate load-balancing (routing) schemes. However, it is unclear whether coding or replication is better from a system performance perspective since the corresponding queueing analysis of such systems is, in general, quite difficult except for the trivial case when the system load asymptotically tends to zero. Here, we study the more difficult case where the system load is not asymptotically zero. Using the fact that the system size is large, we obtain a mean-field limit for the steady-state distribution of the number of file access requests waiting at each server. We then use the mean-field limit to show that, for a given storage capacity per file, coding strictly outperforms replication at all traffic loads while improving reliability. Further, the factor by which the performance improves in the heavy traffic is at least as large as in the light-traffic case. Finally, we validate these results through extensive simulations.

Original languageEnglish (US)
Article number3
JournalACM Transactions on Modeling and Performance Evaluation of Computing Systems
Volume3
Issue number1
DOIs
StatePublished - Feb 2018

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Keywords

  • Cloud storage systems
  • File coding
  • Heavy-traffic analysis
  • Load-balancing
  • Mean-field-analysis

ASJC Scopus subject areas

  • Computer Science (miscellaneous)
  • Computer Networks and Communications
  • Hardware and Architecture
  • Information Systems
  • Software
  • Safety, Risk, Reliability and Quality
  • Media Technology

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