Object Allocation in Distributed Databases and Mobile Computers

This paper makes two contributions. First, we introduce a model for evaluating the performance of data allocation and replication algorithms in distributed databases. The model is comprehensive in the sense that it accounts for I/O cost, for communication cost, and for limits on the minimum number of copies of the object (to ensure availability). The second contribution of this paper is the introduction and analysis of an algorithm for automatic dynamic allocation of replicas to processors. Using the new model, we compare the performance of the traditional read-one-write-all static allocation algorithm, to the performance of the dynamic allocation algorithm. As a result, we obtain the relationship between the communication cost and I/O cost for which static allocation is superior to dynamic allocation, and the relationships for which dynamic allocation is superior.