1 MSCS 237 Introduction to Distributed Systems

2 Outline Distributed computing (DC) Distributed Systems (DS) Motivation Architecture of a DS Advantages

3 Distributed Computing (DC) Distributed computing is a science which solves a large problem by giving small parts of the problem to many computers to solve and then combining the solutions for the parts into a solution for the problem.

4 Distributed Systems (DS) Consists of several computers that do not share memory or a clock Computers communicate with each other by exchanging messages over a communication network Each computer has its own memory Each computer runs its own operating systems The resources owned and controlled by a computer are said to be local to it The resources owned and controlled by other computers and those that can be accessed through the network are said to be remote The terms computer, node, host, site, machines, processor and work station are used interchangeably

5 Motivation Powerful stand alone systems satisfies user needs by providing bit mapped display and visual interfaces, which traditional time sharing mainframe systems do not support Significant advances in communication technologies When a group of people work together, they need to communicate, to share data, to share expensive resources

6 Motivation (cont.) Designing interconnecting computers and resources is feasible –with the availability of cheap and powerful micro processors and –advances in communication technology Interconnected computers have enormous power but cost is only few thousands dollars compare to a single machine of Million dollar Main advantage is decisive power/performance advantage over traditional time sharing systems

7 Architecture of a Distributed Systems (DS) IBM Compatible Workstation Server Laptop computer Hand held computer Tower PCCell phone Communication network Infrastructure based network (wired/wire less) Infrastructure based network (short range wire less)

8 Advantages of DS over traditional time sharing systems Resource sharing Enhanced performance Improved reliability and availability Modular expandability