Electrical Engineering
      and Computer Sciences

Electrical Engineering and Computer Sciences


UC Berkeley


2009 Research Summary

Network Coding for Distributed Storage in Data Centers and Peer-to-Peer Networks

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Georgios Alexandros Dimakis, Philip Brighten Godfrey, Kannan Ramchandran, Martin Wainwright and Yunnan Wu

National Science Foundation CCF-0330514 and Microsoft Graduate Research Fellowship

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.

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 uses slightly larger fragments than MDS but has lower overall bandwidth use. We also show through simulation that in realistic environments, Regenerating Codes can reduce maintenance bandwidth use by 25% or more compared with the best previous design--a hybrid of replication and erasure codes--while simplifying system architecture.

A. G. Dimakis, V. Prabhakaran, and K. Ramchandran, "Ubiquitous Access to Distributed Data in Large-Scale Sensor Networks through Decentralized Erasure Codes," Symposium on Information Processing in Sensor Networks (IPSN '05), 2005.
A. G. Dimakis, P. B. Godfrey, M. Wainwright, and K. Ramchandran, "Network Coding for Distributed Storage Systems," Infocom, 2007.