Network Coding for Distributed Storage Systems

TL;DR

This paper introduces new coding schemes, including Regenerating Codes, for distributed storage systems that significantly reduce bandwidth during maintenance while maintaining reliability.

Contribution

It presents a general analysis framework and two novel schemes for efficient redundancy maintenance using erasure codes in distributed storage.

Findings

Regenerating Codes reduce maintenance bandwidth by over 25% compared to previous methods.

The proposed schemes simplify system architecture while maintaining data reliability.

The analysis framework applies to various coding and replication strategies.

Abstract

Peer-to-peer distributed storage systems provide reliable access to data through redundancy spread over nodes across the Internet. A key goal is to minimize the amount of bandwidth used to maintain that redundancy. Storing a file using an erasure code, in fragments spread across nodes, promises to require less redundancy and hence less maintenance bandwidth than simple replication to provide the same level of reliability. However, since fragments must be periodically replaced as nodes fail, a key question is how to generate a new fragment in a distributed way while transferring as little data as possible across the network. In this paper, we introduce a general technique to analyze storage architectures that combine any form of coding and replication, as well as presenting two new schemes for maintaining redundancy using erasure codes. First, we show how to optimally generate MDS fragments directly from existing fragments in the system. Second, we introduce a new scheme called Regenerating Codes which use slightly larger fragments than MDS but have lower overall bandwidth use. We also show through simulation that in realistic environments, Regenerating Codes can reduce maintenance bandwidth use by 25 percent or more compared with the best previous design--a hybrid of replication and erasure codes--while simplifying system architecture.