Double Regenerating Codes for hierarchical data centers

Data centers increasingly adopt erasure coding to ensure fault-tolerant storage with low redundancy, yet the hierarchical nature of data centers incurs substantial oversubscribed cross-rack bandwidth in failure repair. We present Double Regenerating Codes (DRC), whose idea is to perform two-stage regeneration, so as to minimize the cross-rack repair bandwidth for a single-node repair with the minimum storage redundancy. We prove the existence of a DRC construction, and show via quantitative comparisons that DRC significantly reduces the cross-rack repair bandwidth of state-of-the-art minimum storage regenerating codes.