We consider the resource allocation problem in distributed computing systems that have strict mutual consistency requirements. Our model incorporates the behavior of consistency control algorithms, which ensure that mutual consistency of replicated data is preserved even when communication links of the computer network and/or computers on which the files reside fail. The problem of resource allocation in these networks is significant in terms of the efficiency of operations and the reliability of the network. The constrained resource allocation problem is formulated as a mixed nonlinear integer program. An efficient algorithm is proposed to solve this problem. The performance of the algorithm is evaluated in terms of the algorithm's accuracy, efficiency and execution times, using a representative problem set. 1 Introduction Consider a distributed computing system (DCS) that is made up of a set of sites (nodes) connected through communication links which transmit information from one s...

We consider the consistency control problem for replicated data in a distributed computing system (DCS) and propose a new algorithm to dynamically regenerate copies of data objects in response to node failures and network partitioning in the system. The DCS is assumed to have strict consistency constraints for data object copies. The new algorithm combines the advantages of voting based algorithms and regeneration mechanisms to maintain mutual consistency of replicated data objects in the case of node failures and network partitioning. Our algorithm extends the feasibility of regeneration to DCS on wide area networks, and is able to satisfy user queries as long as there is one current partition in the system. A stochastic availability analysis of our algorithm shows that it provides improved availability as compared to previously proposed dynamic voting algorithms. 1 Introduction In a distributed computing environment, two types of failures may occur: the processor at a given site may...

A consistency control algorithm for replicated data objects in distributed computing systems, called RVC2, has been extensively analyzed. RVC2 is a voting-based algorithm which utilizes a selective regeneration and recovery mechanism for failed copies of data objects. Virtual copies, which record information about the current state of a copy, but which contain no actual data, are used in addition to real copies to reduce network and storage overhead. A theoretical analysis of the algorithm under normal and exceptional conditions, in terms of the message cost, is presented. The results show that RVC2 has a high message cost under some conditions. Empirical results concerning availability, obtained through simulation, are also discussed. These results show that varying the number of real versus virtual copies, and varying the generation threshold, has no significant impact on availability. The results also suggest that RVC2 is an unnecessarily complex algorithm because regeneration has no significant impact on availability under most circumstances. 1.