Reducing costs in the personal cloud: Is bittorrent a better bet?

Lately Personal Cloud storage services, like Drop-box, have emerged as user-centric solutions that provide easy management of the users´ data. To meet the requirements of their clients, such services require a huge amount of storage and bandwidth. In an attempt to reduce these costs, we focus on maximizing the benefit that can be driven from the interest of users in the same content by the introduction of the BitTorrent protocol. In general, it is assumed that BitTorrent is only effective for large files and/or large swarms, while the client-server approach is more suited for small files and/or small swarms. However, there is no concrete study on the comparative efficiency of both protocols for small files yet. In this paper, we study the download time and offload ratio in BitTorrent compared to HTTP. Based on this study, we propose an algorithm for the management of these protocols. The choice of the protocol is made based on the prediction of the efficiency of BitTorrent and HTTP for each case. We validate our algorithm on a real trace of the Ubuntu One file service, achieving important savings in the cloud bandwidth without degrading the download time.