PERFORMANCE OPTIMIZATION OF PARALLEL-DISTRIBUTED PROCESSING WITH CHECKPOINTING FOR CLOUD ENVIRONMENT

摘要

In cloud computing, the most successful application framework is parallel-distributed processing, in which an enormous task is split into a number of subtasks and those are processed independently on a cluster of machines referred to as workers. Due to its huge system scale, worker failures occur frequently in cloud environment and failed subtasks cause a large processing delay of the task. One of schemes to alleviate the impact of failures is checkpointing method, with which the progress of a subtask is recorded as checkpoint and the failed subtask is resumed by other worker from the latest checkpoint. This method can reduce the processing delay of the task. However, frequent checkpointing is system overhead and hence the checkpoint interval must be set properly. In this paper, we consider the optimal number of checkpoints which minimizes the task-processing time. We construct a stochastic model of parallel-distributed processing with checkpointing and approximately derive explicit expressions for the mean task-processing time and the optimal number of checkpoints. Numerical experiments reveal that the proposed approximations are sufficiently accurate on typical environment of cloud computing. Furthermore, the derived optimal number of checkpoints outperforms the result of previous study for minimizing the task-processing time on parallel-distributed processing.