Object Replication in Distributed Web Server Systems with a Hybrid Tabu Search Algorithm

One of the key issues in the design of a distributed web server system (DWS) is determining the optimal number of replicas and their placement on the web servers. This paper presents a hybrid tabu search (HTS) algorithm for replica placement in a DWS environment. We model the object replication problem as a 0-1 optimization problem and specialize the tabu search into a specific algorithm for solving this problem by turning the abstract concepts of tabu search, such as initial solution, solution space, neighborhood, etc, into more concrete, problem specific and implementable definitions. In addition, we hybridize the tabu search algorithm with simulated annealing algorithm to speed up the convergence time of the algorithm without compromising the solution quality. Through a simulation study and comparison with well-known replica placement algorithms, we demonstrate the applicability and effectiveness of our hybrid algorithm.

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