Replication Strategies for Highly Available Peer-to-Peer Storage

In the past few years, peer-to-peer networks have become an extremely popular mechanism for large-scale content sharing. Unlike traditional client-server applications, which centralize the management of data in a few highly reliable servers, peer-to-peer systems distribute the burden of data storage, computation, communications and administration among thousands of individual client workstations. While the popularity of this approach, exemplified by systems such as Gnutella [28.3], was driven by the popularity of unrestricted music distribution, newer work has expanded the potential application base to generalized distributed file systems [28.1], [28.4], persistent anonymous publishing [28.5], as well as support for high-quality video distribution [28.2]. The wide-spread attraction of the peer-to-peer model arises primarily from its potential for both low-cost scalability and enhanced availability. Ideally a peer-to-peer system could efficiently multiplex the resources and connectivity of its workstations across all of its users while at the same time protecting its users from transient or persistent failures in a subset of its components.