Competitive Hill-Climbing Strategies for Replica Placement in a Distributed File System

  • Authors:
  • John R. Douceur;Rogert Wattenhofer

  • Affiliations:
  • -;-

  • Venue:
  • DISC '01 Proceedings of the 15th International Conference on Distributed Computing
  • Year:
  • 2001

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Abstract

The Farsite distributed file system stores multiple replicas of files on multiple machines, to provide file access even when some machines are unavailable. Farsite assigns file replicas to machines so as to maximallyexploit the different degrees of availabilityof different machines, given an allowable replication factor R. We use competitive analysis and simulation to study the performance of three candidate hillclimbing replica placement strategies, MinMax, MinRand, and RandRand, each of which successivelyexc hanges the locations of two file replicas. We show that the MinRand and RandRand strategies are perfectlycomp etitive for R = 2 and 2/3-competitive for R = 3. For general R, MinRand is at least 1/2-competitive and RandRand is at least 10/17-competitive. The MinMax strategyis not competitive. Simulation results show better performance than the theoretic worst-case bounds.