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arXiv 1301.7693cs.ITmath.IT
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最优局部可修码及其与拟阵理论的联系

Optimal Locally Repairable Codes and Connections to Matroid Theory

Itzhak Tamo, Dimitris S. Papailiopoulos, Alexandros G. Dimakis

摘要:

PB级分布式存储系统目前正在向擦除码过渡,以实现更高的存储效率。像Reed-Solomon这样的经典代码对于分布式环境来说是非常次优的,因为它们在单一故障事件中的开销很高。局部可修码是一类新的具有修复效率的码族。特别是,LRC最小化参与单个节点修复的节点的数量,在此期间,它们生成小的网络流量。两个大规模分布式存储系统已经实现了不同类型的LRC:Windows Azure存储和Facebook使用的Hadoop分布式文件系统RAID。LRC的基本界限,即给定代码局部性的最佳可能距离,是最近发现的,但很少有明确的结构存在。在这项工作中,我们提出了一个明确的和最佳的LRC,是简单的构造。我们的建设是基于分组里德所罗门(RS)编码符号,以获得RS编码符号在一个更大的有限域。然后,我们将这些RS符号分成小组,并使用简单的本地代码重新编码它们,提供低修复局部性。为了分析码的最优性,我们得到了关于由代码生成器矩阵表示的拟阵的一个新结果。

英文摘要:

Petabyte-scale distributed storage systems are currently transitioning to erasure codes to achieve higher storage efficiency. Classical codes like Reed-Solomon are highly sub-optimal for distributed environments due to their high overhead in single-failure events. Locally Repairable Codes (LRCs) form a new family of codes that are repair efficient. In particular, LRCs minimize the number of nodes participating in single node repairs during which they generate small network traffic. Two large-scale distributed storage systems have already implemented different types of LRCs: Windows Azure Storage and the Hadoop Distributed File System RAID used by Facebook. The fundamental bounds for LRCs, namely the best possible distance for a given code locality, were recently discovered, but few explicit constructions exist. In this work, we present an explicit and optimal LRCs that are simple to construct. Our construction is based on grouping Reed-Solomon (RS) coded symbols to obtain RS coded symbols over a larger finite field. We then partition these RS symbols in small groups, and re-encode them using a simple local code that offers low repair locality. For the analysis of the optimality of the code, we derive a new result on the matroid represented by the code generator matrix.

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