Load sharing in distributed computer systems

PhD ThesisIn this thesis the problem of load sharing in distributed computer systems is investigated. Fundamental issues that need to be resolved in order to implement a load sharing scheme in a distributed system are identified and possible solutions suggested. A load sharing scheme has been designed and implemented on an existing Unix United system. The performance of this load sharing scheme is then measured for different types of programs. It is demonstrated that a load sharing scheme can be implemented on the Unix United systems using the existing mechanisms provided by the Newcastle Connection, and without making any significant changes to the existing software. It is concluded that under some circumstances a substantial improvement in the system performance can be obtained by the load sharing scheme.Science and Engineering Research Counci

UML Modeling of Network Topologies for Distributed Computer System

Nowadays distributed computer systems have become very popular approach due to its availability at low cost and high performance computers, which are connected through a communication network. For connection of the distributed computer systems, network topologies are must for the communication lines. In the present paper a detailed study of network topologies is done for the distributed computer systems. A most popular Unified Modeling Language (UML) is used for designing the different network topologies. A comparative study is done for 2D Mesh, Torus, and Hypercube topologies and performance is evaluated after designing the UML Class, Sequence, and Activity diagrams for these topologies

DYNAMIC FILE MIGRATION IN DISTRIBUTED COMPUTER SYSTEMS

In a distributed computer system files are shared by both local users and remote users for query and update purposes. A user performing data processing activities tends to reference the same file for some time. When the referenced file is stored remotely, large amounts of communication traffic will be generated. For example, when a customer is making a travel plan, an airline reservation database might be accessed repeatedly by a remote operation site. The inquiries will probably all be made within the time of an ordinary telephone conversation. In many recent developments in distributed computer systems, file migration operations are incorporated into the procedures for processing remote file access requests. Using file migration operations a file may be duplicated or moved to the requesting site in order to reduce communication traffic. As a result, the system is faced with dynamic file placement decisions using a file migration policy. In particular, a file migration policy is expressed as the IF-THEN rules that specify the file migration operations to be implemented at each viable system state. Based on this policy, file migration operations are triggered when the specified conditions are satisfied, and thus dynamically respond to system needs. Because of the dynamic behaviors of systems, the problem of deriving effective file migration policies is extremely complex. An elaborate analysis is required. This paper studies the impact of file migration operations on system performance and develops automatic mechanisms for incorporating file migrations as part of system operations. The mechanisms include optimization models formulated in the form of Markov decision models for deriving optimal file migration policies at system design or redesign points, and heuristic rules to generate adaptive file migration decisions for individual file access requests. The trade-off between these two types of mechanisms is clearly that of performance levels versus implementation complexities. The optimization analysis not only generates the best possible solutions, but provides insight into the problem structure, whereas the rationale for developing heuristics is their simplicity in implementation and acceptable performance levels

A new taxonomy for distributed computer systems based upon operating system structure

Characteristics of the resource structure found in the operating system are considered as a mechanism for classifying distributed computer systems. Since the operating system resources, themselves, are too diversified to provide a consistent classification, the structure upon which resources are built and shared are examined. The location and control character of this indivisibility provides the taxonomy for separating uniprocessors, computer networks, network computers (fully distributed processing systems or decentralized computers) and algorithm and/or data control multiprocessors. The taxonomy is important because it divides machines into a classification that is relevant or important to the client and not the hardware architect. It also defines the character of the kernel O/S structure needed for future computer systems. What constitutes an operating system for a fully distributed processor is discussed in detail

Software metrics: Software quality metrics for distributed systems

Software quality metrics was extended to cover distributed computer systems. Emphasis is placed on studying embedded computer systems and on viewing them within a system life cycle. The hierarchy of quality factors, criteria, and metrics was maintained. New software quality factors were added, including survivability, expandability, and evolvability

CONCEPTS OF DYNAMIC CONTROL OVER DISTRIBUTED COMPUTER SYSTEMS FUNCTIONALITY

To reach the effective organization of distributed computational processes it is important to provide the functionality at the level appropriate for guaranteed and successful execution of computational processes of the task being solved.Solving the problem of distributed computer systems (DCS) functionality provision has become particularly acute in connection with following factors. DCS has become a popular instrument; distributed computation nowadays is becoming a widely used instrument to solve different classes of practical tasks