Building a Strongly Consistent Multi-site File System

A distributed file system provides transparent access to files stored at multiple remote sites. State-of-the-art approaches typically provide weak consistency guarantees in order to comply with the limitations formalized by the CAP theorem. However, weak consistency is tailored for domain-specific applications, where system designers can anticipate conflicts and devise appropriate resolution mechanisms. We believe that strong consistency is more suitable for a general-purpose application like a file system. Our goal is to build a geographically-distributed file system that guarantees strong consistency despite failures. The key mechanism behind our approach is to partition state such that the number of operations that need to be totally ordered across geographically distant sites is minimized.