Section: Software

Pastis: A peer-to-peer file system

Participants : Pierre Sens [ correspondent ] , Jean-Michel Busca.

Pastis is a distributed multi-writer file system. It aims at making use of the aggregate storage capacity of hundreds of thousands of PCs connected to the Internet by means of a completely decentralized peer-to-peer (P2P) network. Replication allows persistent storage in spite of a highly transient node population, while cryptographic techniques ensure the authenticity and integrity of file system data.

Routing and data storage in Pastis are handled by the Pastry routing protocol and the PAST distributed hash table (DHT). The good locality properties of Pastry/PAST allow Pastis to minimize network access latencies, thus achieving a good level of performance when using a relaxed consistency model. Moreover, Pastis does not employ heavy protocols such as BFT (Byzantine Fault Tolerance), like other P2P multi-writer file systems do. In Pastis, for a file system update to be valid, the user must provide a certificate signed by the file owner which proves that he has write access to that file.