Replication, history, and grafting in the Ori file system

TLDR

Ori is a peer‑to‑peer file system that manages user data across multiple devices, providing synchronization, offline access, and backup‑like snapshots by replicating file‑system history, leveraging abundant storage to overcome WAN bandwidth limits. The authors introduce grafting, a mechanism that enables cross‑file‑system data sharing while preserving file‑system history. Grafting links distinct file‑system histories so that changes propagate across systems while maintaining each system’s history. Evaluation shows Ori incurs lower overhead than a FUSE loopback driver locally, and over a WAN it outperforms NFS over a LAN.

Abstract

Ori is a file system that manages user data in a modern setting where users have multiple devices and wish to access files everywhere, synchronize data, recover from disk failure, access old versions, and share data. The key to satisfying these needs is keeping and replicating file system history across devices, which is now practical as storage space has outpaced both wide-area network (WAN) bandwidth and the size of managed data. Replication provides access to files from multiple devices. History provides synchronization and offline access. Replication and history together subsume backup by providing snapshots and avoiding any single point of failure. In fact, Ori is fully peer-to-peer, offering opportunistic synchronization between user devices in close proximity and ensuring that the file system is usable so long as a single replica remains. Cross-file system data sharing with history is provided by a new mechanism called grafting. An evaluation shows that as a local file system, Ori has low overhead compared to a File system in User Space (FUSE) loopback driver; as a network file system, Ori over a WAN outperforms NFS over a LAN.