1.Introduction
Computing Models
i) Desktop Computing
A desktop computer is a personal computer designed for regular use at a single location on or near a desk or table due to its size and power requirements. The most common configuration has a case that houses the power supply, motherboard (a printed circuit board with a microprocessor as the central processing unit (CPU),memory, bus, and other electronic components), disk storage (usually one or more hard disk drives, optical disc drives, and in early models a floppy disk drive); a keyboard and mouse for input; and a computer monitor, speakers, and, often, a printer for output. The case may be oriented horizontally or vertically and placed either underneath, beside, or on top of a desk.
ii) Client-Server Model
Client–server model is a distributed application structure that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients.Often clients and servers communicate over a computer network on separate hardware, but both client and server may reside in the same system. A server host runs one or more server programs which share their resources with clients. A client does not share any of its resources, but requests a server’s content or service function. Clients therefore initiate communication sessions with servers which await incoming requests. Examples of computer applications that use the client–server model are Email, network printing, and the World Wide Web.
Example: When a bank customer accesses online banking services with a web browser (the client), the client initiates a request to the bank’s web server. The customer’s login credentials may be stored in a database, and the web server accesses the database server as a client. An application server interprets the returned data by applying the bank’s business logic, and provides the output to the web server. Finally, the web server returns the result to the client web browser for display.
Problem:Traffic congestion has always been a problem in the paradigm of C / S. When a
large number of simultaneous clients send requests to the same server might cause many problems for this (to more customers, more problems for the server).
iii) Cluster Computing
Cluster computing is used to overcome the problems that occurs with client server
computing.Suppose a business have a huge no. of clients then in such a case a single server is not able to handle the entire load.So, in such a case cluster computing helps to manage the operations. A computer cluster is a set of loosely or tightly connected computers that work together so that, in many respects, they can be viewed as a single system. Unlike grid computers,computer clusters have each node set to perform the same task, controlled and scheduled by software.The components of a cluster are usually connected to each other through fast local area networks, with each node (computer used as a server) running its own instance of an operating system. In most circumstances, all of the nodes use the same hardware[better source needed] and the same operating system, although in some setups (e.g. using Open Source Cluster Application Resources (OSCAR)), different operating systems can be used on
each computer, or different hardware.Clusters are usually deployed to improve
performance and availability over that of a single computer, while typically being much
more cost-effective than single computers of comparable speed or availability.
Examples include the IBM General Parallel File System, Microsoft’s Cluster Shared Volumes or the Oracle Cluster File System.
iv) Grid Computing
Grid Computing is the use of widely distributed computer resources to reach a common goal. The grid can be thought of as a distributed system with non-interactive workloads that involve a large number of files. Grid computing is distinguished from conventional high-performance computing systems such as cluster computing in that grid computers have each node set to perform a different task/application. Grid computers also tend to be more heterogeneous and geographically dispersed (thus not physically coupled) than cluster computers. Although a single grid can be dedicated to a particular application, commonly a grid is used for a variety of purposes. Grids are often constructed with general-purpose grid middleware software libraries.
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