Research On Grid Service Reliability Modeling And Task Scheduling Optimization

With the increase of function and structural complexity of manufacture products, an increased demand of computing and storage ability is needed in product design, which has been beyond the current ability of a single computer. With the emergence of grid technology, people not only can gain more powerful computing power and data storage capacity from Internet, but also can use multiple computers to work together. It can tackle large-scale and difficult problems that would be impossible to feasibly solve using the computing resources of a single organization. However, due to the complexity of grid system, there are a lot of problems unsolved, i.e., grid reliability problem, so that the grid has not been widely used in manufacturing industry and then achieves great changes in industry mode.As one of the important measures of quality of service, grid service reliability can reflect the capacity of providing reliable services from a user's point of view. How to analyze and improve grid service reliability has attracted a lot of research and attention. In this paper, combining grid service reliability analysis with fault tolerance, we study grid service reliability modeling and the reliability-oriented optimization of grid task scheduling. The research can pave the way for thoroughly improving grid service reliability. Firstly, a fault recovery mechanism in grid nodes is introduced and the modeling of grid service reliability considering fault recovery and local task arrivals is studied. Based on the proposed model, an optimization model of grid task scheduling is presented to maximize the grid service reliability. Finally, for the crucial problem of resource pricing in grid task scheduling, a fair price model in market-oriented environment is presented, which can accelerate the grid penetrating into the society.The contributions of this dissertation are summarized as follows:(1) Grid service reliability model with fault recoveryIn order to improve grid service reliability, a fault recovery mechanism in local grid nodes is introduced. Considering fault recovery and software failure, a grid service reliability model is proposed. To make fault recovery more practical, certain constraints on fault recovery, i.e., constraints on the life times of subtasks and on the numbers of recoveries performed, are introduced, and grid service reliability models under these practical constraints are developed. The proposed models can provide an efficient solution for low reliability of time-consuming tasks.(2) Grid task reliability model in manufacturing gridIn manufacturing grid, manufacturing resources have characteristics of autonomy, heterogeneousness and dynamic. They engage tasks coming from not only manufacturing grid system but also the local administrative domain. Especially in the priority strategy of local tasks, the arrival of local task and failure occurrence in the execution of grid task have great impact on the reliable completion of grid task in a specified time. To solve this problem,the state analysis of manufacturing resources based on Petri net is given to describe the complexity of grid task execution process in manufacturing resources. Based on the Monte Carlo Simulation, grid task reliability in the priority strategy of local tasks is obtained. Furthermore, the influence of local task arrival rate and local task execution rate on grid task reliability is analyzed. The results can provide some information to grid resource management so as to make grid task scheduling better.(3) Optimal redundant scheduling of grid tasks based on fault recoveryBased on the proposed grid reliability model, a multi-objective task scheduling optimization model, i.e., minimizing cost and maximizing reliability, is presented and an ant colony optimization algorithm is developed to solve it effectively. Furthermore, to improve grid service reliability, a redundant scheduling strategy of grid tasks is used and an optimization model with a cost constraint is presented to maximize the grid service reliability. A genetic algorithm is developed to solve it and some repair operators are designed to adjust the infeasible solutions of the chromosomes, which can ensure the algorithm work well. A numerical example is given to show the efficiency of the algorithm.(4) Analysis of grid resource compensation in market-oriented environmentMarket-oriented grid resource management is an efficient solution to cope with the scarceness of grid resources in grid system. Through in-depth analysis of this scarceness, it can be known that grid users should pay resource owners a sum of money not only for resources consumed but also for the loss of local task execution. Based on the analysis of the expected incomes of two priority strategies in grid resources, the minimal compensation which grid users should pay to resources owners is determined using the concept of opportunity cost. Based on it, a variable price model is presented to ensure a fair market environment. To calculate minimal compensation, an evaluation approach based on Monte Carlo simulation is given and the minimal compensation can be determined. Furthermore, the influence of the attributes of grid tasks and grid resources on minimal compensation is studied. The research can provide an incentive to resource owners and attract more and more resources in the Internet to participate in the grid.