A Simulation-based Evaluation of a Hybrid Storage System Combining P2P, F2F, and Cloud storage with a Distributed Reputation System

As the amount of valuable data that the average person owns increases, there is a growing need for personal low cost backup services. A variety of methods have been developed to fulfill this need, from cloud based backup services to cooperative methods where users share spare resources to store each other’s data, either using a peer-to-peer (P2P) network to store data among a large number of diverse peers, or a friend-to-friend (F2F) network to store data among a smaller number of trusted friends. There are several advantages to each method, but they all have issues that can make them unsuitable for this task. The purpose of this thesis is to explore the possibility of avoiding these issues by creating a hybrid system that stores files using a combination of cloud storage and trust aware P2P and F2F networks. This should also give the user greater control over the distribution of files and make it more resilient towards malicious peers. A simple file storage system was designed that uses a combined P2P and F2F network together with a reputation system for determining how trustworthy a peer is based on its past behavior, as well as having the option of falling back on cloud storage. The user decides for each file how much data shall be stored using normal peers, friend peers, and cloud storage, and any requirements that the peers used must fulfill. A partial implementation of the system was created as part of a simulator used to evaluate how well the combined P2P and F2F networks and reputation system behaves in various circumstances, and using different distribution policies. While it is difficult to compare the performance of this system to that of other backup and file storage systems without more thorough testing, the results obtained show that it is in fact possible to construct a trust aware hybrid system, that it should perform better than a pure P2P or F2F system, and that it should perform well even if a majority of all peers were to act maliciously.