【摘要】 诸如数字图书馆等规模在1012字节以上的大型数据库需要在线存取大容量磁带库中的海量数据.由于这些需求都是对海量数据的随机存取,而磁带库的随机存取性能很差,所以,研究有效的磁带库随机I/O调度策略和算法是改善磁带库系统性能的重要课题.提出并研究了一种基于效益-代价均衡的调度算法,给出一种有效的效益-代价加权比的估算方法.该算法根据系统的工作负载特点,动态调节调度的效益和代价的加权比,从而改善了磁带库系统在各种负载下的系统性能.研究解决了已有磁带库调度算法的对工作负载敏感的问题,极大改善了调度算法在重负载下的有效性.更多还原

【Abstract】 The terabyte-level (1012 bytes) database systems such as digital libraries need to use tape library as an online device to store and retrieve their massive data. Since the access of a tape library is often random and the tape library has low random access performance, thus it is critical to study the random I/O scheduling strategies and algorithms in order to improve the performance of tape library. In this paper we study a cost-benefit-based scheduling algorithm, and as well as give an effective estimating method of cost-benefit weight ratio. This algorithm improves the performance of tape library system under different workloads by dynamically tuning the cost-benefit weight ratio of scheduling policies according to workloads. This algorithm particularly overcomes the problem of workload-sensitive of existing scheduling algorithms, and is significantly effective under heavy workload.更多还原