Enabling Node Repair in Any Erasure Code for Distributed Storage

TL;DR

This paper introduces a flexible framework that enables traditional erasure codes to efficiently repair failed nodes by reducing the repair process to erasure decoding, combining benefits of various coding schemes.

Contribution

The authors propose a novel framework that allows existing erasure codes to perform efficient node repair, minimizing data download and operational complexity.

Findings

Framework reduces node repair to erasure decoding

Enables traditional codes to achieve repair bandwidth reduction

Supports error detection and correction during repair

Abstract

Erasure codes are an efficient means of storing data across a network in comparison to data replication, as they tend to reduce the amount of data stored in the network and offer increased resilience in the presence of node failures. The codes perform poorly though, when repair of a failed node is called for, as they typically require the entire file to be downloaded to repair a failed node. A new class of erasure codes, termed as regenerating codes were recently introduced, that do much better in this respect. However, given the variety of efficient erasure codes available in the literature, there is considerable interest in the construction of coding schemes that would enable traditional erasure codes to be used, while retaining the feature that only a fraction of the data need be downloaded for node repair. In this paper, we present a simple, yet powerful, framework that does precisely this. Under this framework, the nodes are partitioned into two 'types' and encoded using two codes in a manner that reduces the problem of node-repair to that of erasure-decoding of the constituent codes. Depending upon the choice of the two codes, the framework can be used to avail one or more of the following advantages: simultaneous minimization of storage space and repair-bandwidth, low complexity of operation, fewer disk reads at helper nodes during repair, and error detection and correction.