On Grid Quorums for Erasure Coded Data.

Anwitaman Datta,Frédérique Oggier

doi:10.3390/e23020177

Abstract

We consider the problem of designing grid quorum systems for maximum distance separable (MDS) erasure code based distributed storage systems. Quorums are used as a mechanism to maintain consistency in replication based storage systems, for which grid quorums have been shown to produce optimal load characteristics. This motivates the study of grid quorums in the context of erasure code based distributed storage systems. We show how grid quorums can be built for erasure coded data, investigate the load characteristics of these quorum systems, and demonstrate how sequential consistency is achieved even in the presence of storage node failures.

Highlights

In the context of replication, consistency refers to a setting where read and write operations are performed on shared data by different processes, and it informally means that, when one replica is updated by one of the processes, it should be ensured that the other copies are updated
We refer to Reference [13] for a more detailed treatment of how quorum systems are used in storage applications
The goal of this paper is to study a class of symmetric quorums called grid quorums [13] (Section 3.2), in the context of erasure coded data

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Distributed storage systems store data over a network of nodes, so that data remains available over time. Since failures may be temporary or permanent, redundancy needs to be replenished via maintenance mechanisms, in order to achieve (2), that is persistence over time. Since the data is stored redundantly, it becomes essential to ensure consistency, so that all applications accessing a given data see the same version, in particular after updates, irrespective of which storage nodes are accessed. Both maintenance of adequate level of redundancy and consistency depend on the redundancy mechanisms chosen, which typically induce trade-offs with storage overhead.

Consistency

Related Works

Contributions

Erasure Coding for Storage

Quorum Systems

Quorum Systems and Erasure Coded Data

Basic Grid Quorums

Basic Grid Quorums for Coded Data

B-Grid Quorums for Coded Data

Consistency in Presence of Node Failures

Concluding Remarks