The Impact of Data Replicatino on Job Scheduling Performance in Hierarchical data Grid

In data-intensive applications data transfer is a primary cause of job execution delay. Data access time depends on bandwidth. The major bottleneck to supporting fast data access in Grids is the high latencies of Wide Area Networks and Internet. Effective scheduling can reduce the amount of data transferred across the internet by dispatching a job to where the needed data are present. Another solution is to use a data replication mechanism. Objective of dynamic replica strategies is reducing file access time which leads to reducing job runtime. In this paper we develop a job scheduling policy and a dynamic data replication strategy, called HRS (Hierarchical Replication Strategy), to improve the data access efficiencies. We study our approach and evaluate it through simulation. The results show that our algorithm has improved 12% over the current strategies.Comment: 11 pages, 7 figure

A Taxonomy of Data Grids for Distributed Data Sharing, Management and Processing

Data Grids have been adopted as the platform for scientific communities that need to share, access, transport, process and manage large data collections distributed worldwide. They combine high-end computing technologies with high-performance networking and wide-area storage management techniques. In this paper, we discuss the key concepts behind Data Grids and compare them with other data sharing and distribution paradigms such as content delivery networks, peer-to-peer networks and distributed databases. We then provide comprehensive taxonomies that cover various aspects of architecture, data transportation, data replication and resource allocation and scheduling. Finally, we map the proposed taxonomy to various Data Grid systems not only to validate the taxonomy but also to identify areas for future exploration. Through this taxonomy, we aim to categorise existing systems to better understand their goals and their methodology. This would help evaluate their applicability for solving similar problems. This taxonomy also provides a "gap analysis" of this area through which researchers can potentially identify new issues for investigation. Finally, we hope that the proposed taxonomy and mapping also helps to provide an easy way for new practitioners to understand this complex area of research.Comment: 46 pages, 16 figures, Technical Repor

An Overview of a Grid Architecture for Scientific Computing

This document gives an overview of a Grid testbed architecture proposal for the NorduGrid project. The aim of the project is to establish an inter-Nordic testbed facility for implementation of wide area computing and data handling. The architecture is supposed to define a Grid system suitable for solving data intensive problems at the Large Hadron Collider at CERN. We present the various architecture components needed for such a system. After that we go on to give a description of the dynamics by showing the task flow

Analysis and selection of the simulation environment

This document provides the initial report of the Simulation work package (Work Package 4,WP4) of the CATNETS project. It contains an analisys of the requirements for a simulation tool to be used in CATNETS and an evaluation of a number of grid and general purpose simulators with respect to the selected requirements. A reasoned choice of a suitable simulator is performed based on the evaluation conducted. -- Diese Arbeit analysiert die Anforderungen an eine Simulationsumgebung für die Analyse der Katallaxie. Anhand von Kennzahlen wird die Auswahl der Simulationsumgebung bestimmt.Grid Computing

Analysis of simulation environment

In this paper the requirements for an ALN simulation environment are analysed, as needed in the CATNETS Project. A number of grid and general purpose simulators are evaluated regarding the identified requirements for simulating economical resource allocation mechanisms in ALNs. Subsequently a suitable simulator is chosen for usage in the CATNETS project. --CATNETS simulator,requirements analysis,simulator selection

A data Grid prototype for distributed data production in CMS

The CMS experiment at CERN is setting up a Grid infrastructure required to fulfill the needs imposed by Terabyte scale productions for the next few years. The goal is to automate the production and at the same time allow the users to interact with the system, if required, to make decisions which would optimize performance. We present the architecture, design and functionality of our first working Objectivity file replication prototype. The middle-ware of choice is the Globus toolkit that provides promising functionality. Our results prove the ability of the Globus toolkit to be used as an underlying technology for a world-wide Data Grid. The required data management functionality includes high speed file transfers, secure access to remote files, selection and synchronization of replicas and managing the meta information. The whole system is expected to be flexible enough to incorporate site specific policies. The data management granularity is the file rather than the object level. The first prototype is currently in use for the High Level Trigger (HLT) production (autumn 2000). Owing to these efforts, CMS is one of the pioneers to use the Data Grid functionality in a running production system. The project can be viewed as an evaluator of different strategies, a test for the capabilities of middle-ware tools and a provider of basic Grid functionalities