A peer-to-peer-based storage system has become a common way to alleviate network congestion and the limitation of storage space for providing file sharing, distributed computation, and instant messaging. Since the peer-to-peer technique has been used in file sharing, replications of a file is produced for a quick response and high availability. On the other hand, too much replications of a file may waste storage after the file become unpopular. The objective is to manage replications of file efficiently. In the proposed method, a popularity level is defined for evaluating the popularity of a file, used to determine the increasing or decreasing of the number of replications. The popularity level has three thresholds to determine replication of file. Thresholds are setting up by the 80-20 rule, and it changes dynamically overtime. We conclude that the popularity of file and its number of replication affect each other to use storage efficiently.