主动容错云存储系统的可靠性评价模型

除了传统的冗余机制，主动容错技术也被用来提高存储系统的可靠性。然而，当前对主动容错云存储系统可靠性的研究工作很少，而且都局限于硬盘故障服从指数分布的假设前提。针对主动容错磁盘冗余阵列RAID-5和RAID-6云存储系统提出两个可靠性状态转移模型，并基于转移模型设计了蒙特卡洛仿真算法，评价系统在一定运行周期内发生数据丢失事件的期望个数。该算法采用韦布分布函数模拟随时间变化（降低、恒定不变、或升高）的硬盘故障率，准确评价了主动容错机制、硬盘整体故障、故障修复、潜在块故障以及磁盘清洗过程对系统可靠性的影响。所提方法可以帮助系统设计者评估不同容错机制和系统参数对云存储系统可靠性的影响，有助于创建高可靠存储系统。

Reliability evaluation model for cloud storage systems with proactive fault tolerance

In addition to traditional reactive fault-tolerant technologies, proactive fault tolerance can be used to improve storage system reliability significantly. There is few research on reliability of proactive cloud storage systems, supposing exponential distribution of drive failure. Two reliability state transfer models were developed for proactive redundant arrays of independent disks RAID-5 and RAID-6 systems respectively. Based on the models, Monte Carlo simulations were designed to estimate the expected number of data-loss events in proactive RAID-5 and RAID-6 systems within a given time period. Weibull distribution was used to model time-based (decreasing, constant occurrence, or increasing) disk failure rates, and express the impact of proactive fault tolerance, operational failures, failure restoration, latent block defects, and drive scrubbing on the system's reliability. The proposed method can help system designers to evaluate the impact of different fault tolerance mechanisms and system parameters on the reliability of cloud storage systems, and help to create highly reliable storage systems.