Duplicacy: A New Generation of Cloud Backup Tool Based on Lock-Free Deduplication

The pervasive deployment of cloud services poses an ever-increasing demand for cross-client deduplication solutions to save network bandwidth, lower storage costs, and improve backup speeds. However, existing solutions typically depend on lock-based approaches relying on a centralized chunk database, which tends to hinder performance scalability. In this article, we present a new cross-client cloud backup solution, named Duplicacy, based on a Lock-Free Deduplication approach. Lock-Free Deduplication stores chunks to network or cloud storage using content hashes as file names. It then adopts a two-step fossil deletion algorithm to solve the hard problem of deleting unreferenced chunks in the presence of concurrent backups, without the need for any locks. Experiments demonstrate that Duplicacy enables significant performance improvement for backups over previous well-known backup tools. In addition, Duplicacy can work with many general-purpose network or cloud storage services which only support a basic set of file operations, and turn them into sophisticated deduplication-aware storage servers without server-side changes.