云存储中动态副本放置机制研究

数据副本管理是云计算系统管理的重要组成部分,在云计算系统的海量数据处理过程中,针对目前已知的数据存放与资源调度算法存在考虑副本动态性和可靠性的不足,提出了一种动态的副本放置机制。该机制基于区域结构,考虑数据处理时其副本的数量和放置位置,以及副本的产生对于内存和带宽等系统资源的开销:首先根据云存储中的副本信息,对被访问频率高且访问平均响应时间长的数据信息进行复制,并给出副本数量的计算方法;考虑缩小副本分布的节点选择范围,提出动态的副本放置算法——DRA,将一定范围内的节点根据提出的域的划分,进行放置筛选,以存放数据副本。实验结果表明,提出的动态放置机制不仅减少了低访问率副本对系统存储空间的浪费;同时也减少了高访问率副本所需跨节点的传输延迟,有效提高了云存储系统中的数据文件的访问效率、负载的均衡水平,以及云存储系统的可靠性和可用性。

A dynamic replication placementmechanism in cloud storage

Data replica management is an important part of cloud computing system. When processing massive data in a cloud computing system, the existing algorithms for data storage and resource scheduling do not consider the dynamics and reliability of data replicas．We therefore propose a dynamic replica placement mechanism based on the domain structure. It takes into full account the number and position of data replicas, as well as the cost of system resources such as memory and bandwidth when a replica is produced. Firstly, according to the information of the replica, the data with high access frequency and long average response time, are replicated, and how to calculate the number of replicas is explained. Secondly, in order to reduce the selection range of nodes of the replica distribution, we propose a dynamic replica placement algorithm, which can choose the range of placement for the replicas according to domain division. Experimental results show that the proposed algorithm can significantly reduce the waste of storage space for the replica with low access frequency, as well as the transmission delay across nodes for the replicas with high access frequency. Besides, it effectively improves the access efficiency to data files in cloud storage systems, the load balance, and the reliability and availability of cloud storage systems.