08-16-2017, 10:02 PM
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Presented By
Shrilatha suvarna B.(4nm03mca75
INTRODUCTION
Computer architectures consisting of interconnected, multiple processors are basically of two types:
1). Tightly coupled system
2). Loosely coupled system
Tightly coupled systems
In these systems, there is a single system wide primary memory (address space) that is shared by all the processors . Usually tightly coupled systems are referred to as parallel processing systems.
Loosely coupled systems
In these systems, the processors do not share memory, and each processor has its own local memory .Loosely coupled systems are referred to as distributed computing systems, or simply distributed systems
DEFINITION
A distributed computing system is basically a collection of processors interconnected by a communication network in which each processor has its own local memory and other peripherals, and the communication between any two processors of the system takes place by message passing over the communication network
Advantages Of Distributed Computing System
Inherently Distributed applications:
several applications are inherently distributed in nature and require distributed computing system for their realization
Information Sharing among Distributed Users:
In a distributed computing system, information generated by one of the users can be easily and efficiently shared by the users working at other nodes of the system .The use of distributed computing systems by a group of users to work cooperatively is known as computer-supported cooperative working (CSCW), or groupware .
Resource Sharing:
Information is not the only thing that can be shared in a distributed computing system. Sharing of software resources such as software libraries and databases as well as hardware resources such as printers, hard disks, and plotters can also be done in a very effective way among all the computers and the users of a single distributed computing system.
Extensibility and Incremental Growth:
It is possible to gradually extend the power and functionality of a distributed computing system by simply adding additional resources (both hardware and software) to the system as and when the need arises . Incremental growth is very attractive feature because for most existing and proposed applications it is practically impossible to predict future demands of the system. Extensibility is also easier in a distributed computing system because addition of new resources to an existing system can be performed without significant disruption of the normal functioning of the system.
Shorter Response Times and Higher Throughput:
The multiple processors of the distributed computing system can be utilized properly for providing shorter response times and higher throughput than a single processor centralized system. Another method often used in distributed computing systems for achieving better overall performance is to distribute the load more evenly among the multiple processors by moving the jobs from currently overloaded processors to lightly loaded ones
Higher Reliability:
Reliability refers to the degree of tolerance against errors and component failures in a system. A reliable system prevents loss of information even in the event of component failures An important aspect of reliability is availability, which refers to the fraction of time for which a system is available for use.
Better Flexibility in Meeting User s Needs:
Performing different types of computers are usually more suitable for different types of computation. A distributed computing system may have a pool of different types of computers, in which case the most appropriate one can be selected for processing a user s job depending on the nature of the job.
Better Price-Performance Ratio:
With the rapidly increasing power and reduction in prize of the microprocessors, combined with the increasing speed of communication network, distributed computing systems potentially have a much better price performance ratio than a single large centralized system. More cost-effective Then the centralized system is that they facilitate resource sharing among multiple computers
CONCLUSION
Despite the increased complexity and the difficulty of building distributed computing systems, the installation and the use of distributed computing systems are rapidly increasing. This is mainly because the advantages of distributed computing systems overcome their disadvantages.