Availability of coding based replication schemes

IEEE Transactions on Parallel and Distributed Systems, 1995

Data is often replicated in distributed systems to improve availability and performance. This replication is expensive in terms of disk storage since the existing schemes generally require full files to be stored at each site. In this paper, we present schemes which significantly reduce the storage requirements in replication based systems. These schemes use the coding method suggested by Rabin to store replicated data. The first scheme that we present is a modification of the simple voting algorithm and its quorum requirements. , We then show how some of the extensions of the voting algorithm can also be modified to get storage efficient schemes for managing such replication. We evaluate the availability offered by these schemes and show that the storage space required to achieve certain availability are signiscanfly lower than the conventional schemes with full file replication. Since coding is used, these schemes also provide a high degree of data security.

ArXiv, 2013

Data storage systems are more reliable than their individual components. In order to build highly reliable systems out of less reliable parts, systems introduce redundancy. In replicated systems, objects are simply copied several times with each copy residing on a different physical device. While such an approach is simple and direct, more elaborate approaches such as erasure coding can achieve equivalent levels of data protection while using less redundancy. This report examines the trade-offs in cost and performance between replicated and erasure encoded storage systems.

1992

Abstract A scheme for maintaining replicated files is suggested. The authors describe how the coding scheme suggested by MO Rabin (1987, 1989) can be used to store replicated data and how the voting algorithm and the quorum requirements change to manage this replication. It is shown that the disk storage space required to achieve a given availability is significantly lower than that for the conventional scheme with full file replication. Since coding is used, this scheme also provides a high degree of data security

2011

The necessity of ever-increasing use of distributed data in computer networks is obvious for all. One technique that is performed on the distributed data for increasing of efficiency and reliablity is data rplication. In this paper, after introducing this technique and its advantages, we will examine some dynamic data replication. We will examine their characteristies for some overus scenario and the we will propose some suggestion for their improvement.

2004

Abstract Erasure coding is a technique for achieving high availability and reliability in storage and communication systems. We revisit the analysis of erasure code replication and point out some situations when whole-file replication is preferred. The switchover point (from preferring whole-file replication to erasure code replication) is studied, and characterized using asymptotic analysis. We also discuss the additional considerations in building erasure code replication systems.

1988

Data are often replicated in distributed systems to protect them against site failures and network malfunctions. When this is the case, an access policy must be chosen to insure that a consistent view of the data is always presented. Voting protocols guarantee consistency of replicated data in the presence of any scenario involving non-Byzantine site failures and network partitions. While Static Majority Consensus Voting protocols use static quorums, Dynamic Voting protocols, like Dynamic Voting and Lexicographic Dynamic Voting, dynamically adjust quorums to changes in the status of the network of sites holding the copies.

To improve the availability and reliability of files the data are often replicated at several sites. A scheme must then be chosen to maintain the consistency of the file contents in the presence of site failures. The most commonly used scheme is voting. Voting is popular because it is simple and robust: voting schemes do not depend on any sophisticated message passing scheme and are unaffected by network partitions. When network partitions cannot occur, better availabilities and reliabilities can be achieved with the available copy scheme. This scheme is somewhat more complex than voting as the recovery algorithm invoked after a failure of all sites has to know which site failed last. We present in this paper a new method aimed at finding this site. It consists of recording those sites which received the most recent update ; this information can then be used to determine which site holds the most recent version of the file upon site recovery. Our approach does not require any monitoring of site failures and so has a much lower overhead than other methods. We also derive, under standard Markovian assumptions, closed-form expressions for the availability of replicated files managed by voting, available copy and a naive scheme that does not keep track of the last copy to fail.

Proceedings of the 6th International Conference on …, 1986

Voting schemes ensure the consistency of replicated files by disallowing all read and write requests that cannot collect an appropriate quorum of copies. This procedure requires a minimum number of three copies to be of any practical use and tends to disallow a relatively high number of read and write requests.

Lecture Notes in Computer Science, 1990

Replication can enhance the availability of the data les in a distributed environment. This paper introduces a method for managing replicated data les. Unlike many others, our method provides protocols and algorithms for a more complicated scheme of replication that supports replication with location-variant les and les with a variable degree of replication. We assume the existence of a dynamic le assignment algorithm as well as a block-oriented majority consensus voting approach.

Available copy protocols guarantee the consistency of replicated data objects against any combination of non-Byzantine failures that do not result in partial communication failures. While the original available copy protocol assumed instantaneous detection of failures and instantaneous propagation of this information, more realistic protocols that do not rely on these assumptions have been devised. Two such protocols are investigated in this paper: a naive available copy (NAC) protocol that does not maintain any state information, and an optimistic available copy (OAC) protocol that only maintains state information at write and recovery times. Markov models are used to compare the performance of these two protocols with that of the original available copy protocol. These protocols are shown to perform nearly as well as the original available copy protocol, which is shown to perform much better than quorum consensus protocols.