Apart from high space efficiency, other demanding requirements for enterprise de-duplication backup are high performance, high scalability, and availability for large-scale distributed environments. The main challenge is reducing the significant disk input/output (I/O) overhead as a result of constantly accessing the disk to identify duplicate chunks. Existing inline de-duplication approaches mainly rely on duplicate locality to avoid disk bottleneck, thus suffering from degradation under poor duplicate locality workload. This paper presents Chunkfarm, a post-processing de-duplication backup system designed to improve capacity, throughput, and scalability for de-duplication. Chunkfarm performs de-duplication backup using the hash join algorithm, which turns the notoriously random and small disk I/Os of fingerprint lookups and updates into large sequential disk I/Os, hence achieving high write throughput not influenced by workload locality. More importantly, by decentralizing fingerprint lookup and update, Chunkfarm supports a cluster of servers to perform de-duplication backup in parallel; it hence is conducive to distributed implementation and thus applicable to large-scale and distributed storage systems.

关键词： Backup system,  De-duplication,  Post-processing,  Fingerprint lookup,  Scalability