Data Replication in Cloud Systems: A Survey

This paper presents a survey of data replication strategies in cloud systems. Based on the survey and reviews of existing classifications, we propose another classification of replication strategies based on the following five dimensions: i static vs. dynamic, ii reactive vs. proactive workload balancing, iii provider vs. customer centric, iv optimal number vs. dynamic adjustment of the replica factor and v objective function. Ideally, a good replication strategy must simultaneously consider multiple criteria: i the reduction of access time, ii the reduction of the bandwidth consumption, iii the storage resource availability, iv a balanced workload between replicas and v a strategic placement algorithm including an adjusted number of replicas. Therefore, selecting a data replication strategy is a classic example of multiple criteria decision making problems. The taxonomy we present can be a useful guideline for IT managers to select the data replication strategy for their organization.