Improved results for data migration and open shop scheduling

Abstract

The data migration problem is to compute an efficient plan for moving data stored on devices in a network from one configuration to another. We consider this problem with the objective of minimizing the sum of completion times of all storage devices. Kim [13] gave a 9-approximation algorithm for the problem. We improve Kim's result by giving a 5.06-approximation algorithm. We also address the open shop scheduling problem, O|rj|ΣwjC j, and show that it is a special case of the data migration problem. Queyranne and Sviridenko [18] gave a 5.83-approximation algorithm for the nonpreemptive version of the open shop problem. They state as an obvious open question whether there exists an algorithm for open shop scheduling that gives a performance guarantee better than 5.83. Our 5.06 algorithm for data migration proves the existence of such an algorithm. Crucial to our improved result is a property of the linear programming relaxation for the problem. Similar linear programs have been used for various other scheduling problems. Our technique may be useful in obtaining improved results for these problems as well. © Springer-Verlag Berlin Heidelberg 2004.