Making Wide Stripes Practical: Cascaded Parity LRCs for Efficient Repair and High Reliability

TL;DR

This paper introduces Cascaded Parity LRCs (CP-LRCs), a new wide stripe erasure coding scheme that improves repair efficiency and maintains high reliability by embedding structured dependencies among parity blocks.

Contribution

The paper proposes a novel cascaded parity design for wide stripe LRCs, enabling low-bandwidth repairs and high fault tolerance, with a general framework and practical instantiations.

Findings

Up to 41% reduction in repair time for single-node failures.

Up to 26% reduction in repair time for two-node failures.

Maintains MDS-level fault tolerance with structured parity dependencies.

Abstract

Erasure coding with wide stripes is increasingly adopted to reduce storage overhead in large-scale storage systems. However, existing Locally Repairable Codes (LRCs) exhibit structural limitations in this setting: inflated local groups increase single-node repair cost, multi-node failures frequently trigger expensive global repair, and reliability degrades sharply. We identify a key root cause: local and global parity blocks are designed independently, preventing them from cooperating during repair. We present Cascaded Parity LRCs (CP-LRCs), a new family of wide stripe LRCs that embed structured dependency between parity blocks by decomposing a global parity block across all local parity blocks. This creates a cascaded parity group that preserves MDS-level fault tolerance while enabling low-bandwidth single-node and multi-node repairs. We provide a general coefficient-generation framework, develop repair algorithms exploiting cascading, and instantiate the design with CP-Azure and CP-Uniform. Evaluations on Alibaba Cloud show reductions in repair time of up to 41% for single-node failures and 26% for two-node failures.