Proxy-Assisted Regenerating Codes With Uncoded Repair for Distributed Storage Systems

Distributed storage systems can store data with erasure coding to maintain data availability with low storage redundancy. One class of erasure coding is based on regenerating codes, which provably minimize the amount of data transferred for failure repair and realize the optimal tradeoff between the storage redundancy and the amount of traffic transferred for repair. Typical regenerating codes often require surviving storage nodes to encode their stored data for repair. In this paper, we study a framework called proxy-assisted regeneration, which offloads the repair process to a centralized proxy. We extend the previous applied work on proxy-assisted regeneration by providing theoretical validation. Specifically, we study a special class of regenerating codes called proxy-assisted minimum storage regenerating (PMSR) codes, which enable uncoded repair without the need of encoding in surviving nodes, while preserving the minimum storage redundancy and minimum amount of traffic transferred for repair. We formally prove the existence of PMSR codes for two configurations: 1) repairing single-node failures under double fault tolerance and 2) repairing double-node failures under triple fault tolerance. We also provide a semi-deterministic PMSR code construction for repairing single-node failures under double fault tolerance.