There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The Grid 2: Blueprint for a New Computing Infrastructure

A Systematic Literature Review of the Data Replication Techniques in the Cloud Environments

There are many different replica control techniques, used in different research communities. To understand when one replica management algorithm can be replaced by another, we need to describe more abstractly the consistency model, which captures the set of properties that an algorithm provides, and on which the clients rely (whether the clients are people or other programs). In this chapter we describe a few of the different consistency models that have been proposed, and we sketch a framework for thinking about consistency models. In particular, we show that there are several styles in which consistency models can be expressed, and we also propose some axes of variation among the consistency models.

Consistency Models for Replicated Data.

Summary
Data grid provides an efficient solution for data-oriented applications that need to manage and process large data sets located at geographically distributed storage resources. Data grid relies on data replicas to enhance the performance and to ensure the fault tolerant results to the users. Replicas are developed to increase the availability of data and to provide better data access. Replicas have their own advantages, but there are a number of issues that must be resolved. Among various existing issues, the critical concern is replica consistency. Various replica consistency strategies are available in the literature. These strategies rationalize and investigate various parameters like bandwidth consumption, access cost, scalability, execution time, storage consumption, staleness, and freshness of replicas. In this paper, several asynchronous replica consistencies are classified and analyzed based on various strategies such as topology, level of abstraction, update propagation, and locality. Some other strategies are also discussed and analyzed like adaptive consistency, quorum-based consistency, load balancing, and agent-based economically efficient, check-pointing, fault tolerance, and conflict management. Parameters on which these strategies are analyzed are methodology, replication classification, consistency, grid topology, environment, evaluation parameters, and performance. Copyright © 2016 John Wiley & Sons, Ltd.

Strategies for replica consistency in data grid – a comprehensive survey

In data grids scientific and business applications produce huge volume of data which needs to be transferred among the distributed and heterogeneous nodes of data grids. Data replication provides a solution for managing data files efficiently in large grids. The data replication helps in enhancing the data availability which reduces the overall access time of the file. In this paper an algorithm, namely, EDRA using agents for data grid, has been proposed and implemented. EDRA consists of dynamic replication of hierarchical structure taken into account for the selection of best replica. Decision for selecting the best replica is based on scheduling parameters. The scheduling parameters are bandwidth, load gauge, and computing capacity of the node. The scheduling in data grid helps in reducing the data access time. The distribution of the load on the nodes of data grid is done evenly by considering scheduling parameters. EDRA is implemented using data grid simulator, namely, OptorSim. European Data Grid CMS test bed topology is used in this experiment. The simulation results are obtained by comparing BHR, LRU, No Replication, and EDRA. The result shows the efficiency of EDRA algorithm in terms of mean job execution time, network usage, and storage usage of node.

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Efficient Dynamic Replication Algorithm Using Agent for Data Grid

Grid is collection of heterogeneous resources. The availability and searching the appropriate resources for job execution determine the computing performance of grid. In this paper a model namely ‘Decentralized P2P Grid Resources Discovery’ has been proposed and designed with prototype implementation. This model uses the resources information that is stored in data structure called LC-Trie [1] (Level Compressed Trie). The ring and tree topology has been cross-breaded with combined path and level compression in the proposed model. Proposed model will be evaluated on certain factors like fast retrieval and space complexity etc.

Decentralized P2P Grid Resources Discovery model in LC-Trie structured overlay

Data Grid is emerging as a key technology to support data intensive applications. Grids rely on data replication to enhance performance of the system. Maintaining replicas is the primary concern of replica management in grid environment. This paper addresses the issueof replica creation which in turn enhances the accessibility of updated replica in grid environment. A strategy for Replicas Creation based on Popularity (RCP) has been developed which dynamically creates the replicasin distributed grid environment. An intelligent agent based approach is used which helps in optimizing the number of replicas based on the access frequency of a file. The proposed RCP strategy is implemented on Optorsim simulator and the results are compared with existing approaches to judge its effectiveness in data grids. The simulation results show significant benefits of proposed algorithm in terms of average execution time, number of replica and effective network usage.

Priyanka Vashisht

Papers

Strategies for replica consistency in data grid – a comprehensive survey

Efficient Dynamic Replication Algorithm Using Agent for Data Grid

Decentralized P2P Grid Resources Discovery model in LC-Trie structured overlay

Optimizing Replica Creation using Agents in Data Grids

Agent Based Efficient Consistency Control and Replica Management in Data Grids