A model for optimal database allocation in distributed computing systems

Optimal allocation of redundant resources in distributed computing systems is studied. In the model, the triple module redundancy (TMR) scheme is adopted to enhance the reliability of the operations. A retrieval request from a site for a database will be processed by three database servers. The output results will be obtained by majority voting. The objective is to find the number of database copies and their locations that optimize the total operation cost. Both static and dynamic allocation environments are considered. The problem is formulated as a zero/one integer programming problem. Preliminary test results show that the algorithm has fast convergence and provides a tight lower bound for the optimal operational cost. In particular, it offers high flexibility in terms of termination criteria, which makes it useful in a dynamic allocation environment