A Client-Based Replication Protocol for Multiversion Cloud File Storage

In recent years, data replication have received attention in terms of tolerance for large-scale disasters. Also, file versioning features, by which more than one version of a file can be maintained, have been commercially available in some storage services. For providing file versioning with limited storage resources, it is essential to divide the resources among versions in accordance with the varied needs of numerous users. In this paper, we focus on applications in which newer versions of a file are more likely to be requested, which may be true in the case of many subscription services. We propose a new distributed data replication protocol supporting the file versioning feature. In order to eliminate a single point of failure, replica nodes themselves do not know about which nodes hold the newest version, instead, clients dynamically search the nodes having the required version in read/write operations. We also construct an analytical model that can derive an optimal allocation of the resources when the total number of replica nodes in a system and the distribution of the frequency of read requests for each version are given. In addition, we present some numerical examples obtained by simulations to show the good scalability and dependability of our system by assuming some realistic parameters.