Exploiting network locality in a decentralized read-write peer-to-peer file system

Abstract

We have developed a completely decentralized multiuser read-write peer-to-peer file system with good locality properties. In our system all data is contained in blocks stored using the Past distributed hash table (DHT), thus taking advantage of the fault tolerance and locality properties of Past and Pastry. We have also introduced a modification to the Past DHT which allows us to further increase performance when using a relaxed but nevertheless useful consistency model. Authentication and integrity are assured using standard cryptographic mechanisms. We have developed a prototype in order to evaluate the performance of our design. Our prototype is programmed in Java and uses the FreePastry open-source implementation of Past and Pastry. It allows applications to choose between two degrees of consistency. Preliminary results obtained through simulation suggest that our system is approximately twice as slow as NFS. In comparison, Ivy and Oceanstore are between two to three times slower than NFS.