Hierarchical Erasure coding for P2P storage

The work in this article was motivated by the development of an experimental Peer-to-Peer backup system called Storage Exchange System at Microsoft Live Labs. The data from the peers is encoded using Hierarchical Erasure codes and stored on other peers. Such codes have also been independently described by others. We give a new efficient algorithm that allow us to estimate the availability of the Hierarchically encoded files given an estimate of the availability of the peers. This allows the system to provide a guaranteed lower bound for the availability of the data.