Modeling and Evaluating Peer-to-Peer Storage Architectures

Peer-to-peer storage architecture aims to aggregating the storage of individual computers (peers) to form a universal shared storage space, in which all peers undertake identical roles. The fully distributed nature of such architecture makes it possible to support features such as scalability at a global scale, self-configuration and dynamic adaptation, permanency, fault tolerance, and anonymity. Representative examples include Freenet, OceanStore, PAST and CFS. In this paper, we study the memory architecture of such systems, especially the efforts of caches and directories on the performance. To facilitate the study, an abstract model, called the distributed shared memory (DSM) model, is first proposed to capture the essence of the peer-to-peer storage architecture from the memory perspective. Six variations representing different points in the peer-to-peer storage design space are then identified. Three state-of-the-art peer-to-peer storage systems are cast onto these models and then examined qualitatively. Performance of these models under different memory pressure, network size and failure degree is finally evaluated via simulation.