Task scheduling modelling and reliability evaluation of grid services using coloured Petri nets

The computational grid is a new technology aimed to facilitate resource sharing and wide area collaborations. Task scheduling is an important aspect in the grid environment to obtain a desired quality of service (QoS). In grid environments, the resource management system (RMS) is responsible for the scheduling and execution of tasks. The RMS divides the incoming tasks into several subtasks and distributes them among grid resources for parallel execution. Then, the RMS integrates the received results into the entire task output, which is requested by the user. A grid service is desired to execute a certain task under the control of the RMS. In this paper, the task scheduling by RMS and the task execution within grid resources are modeled using coloured Petri nets (CPNs). The proposed CPN-based modelling pattern formally describes the process of task distribution and execution within the grid environment. We have also proposed a method for evaluation the grid service reliability based on the analysis of the model. In addition, an instance of the proposed model for a sample grid environment is constructed and analysed using CPN Tools. The CPN model and the results of the reliability evaluation of the sample grid environment are also presented in this paper.