MetaSync: Coordinating Storage across Multiple File Synchronization Services

Cloud-based file synchronization services such as Dropbox are a worldwide resource for many millions of users. However, individual services often have tight resource limits, suffer from temporary outages or shutdowns, and sometimes silently corrupt or leak user data. As a solution, the authors design, implement, and evaluate MetaSync, a secure and reliable file synchronization service using multiple cloud synchronization services as untrusted storage providers. To provide global consistency among the storage providers, the authors devise a novel variant of Paxos that enables efficient updates on top of the unmodified APIs exported by each service. MetaSync provides better availability and performance, stronger confidentiality and integrity, and larger storage for end users.