Distributed Systems CS 8603 INTRODUCTION WHAT O TANENBAUM

Distributed Systems CS 8603 INTRODUCTION

WHAT ? O TANENBAUM A distributed system is a collection of independent computers that appears to its users as a single coherent system. 2 Aspects O DS consists of components (i. e. , computers) that are autonomous. O The Second aspect is that users think they are dealing with a single system. This means that one way or the other the autonomous components need to collaborate.

Factors to be considered for creating a DS… O Let us discuss about four important goals for building a distributed system worth the effort O Making Resources Accessible O Distributed Transparency O Openness O Scalability

Making Resources Accessible O As a whole let us consider an example of Bachman Lab and our HOD Room The HOD has a separate Printer and moreover all the other students of third cse who are in bachman lab can be able to take their document print outs from their labs as they will not be provided with the separate printers O Ex Resources : Printers, computers, storage facilities, data, files, Web pages, and networks,

Distributed Transparency A distributed system should look like a single computer system to the users which is said to be transparent. O Types of Transparency 1. Access - Different OS 2. Location - Downloading 3. Migration - Transferring a data from one end to other 4. Relocation - Availability of file , that can move over to locations 5. Replication – Making copies of a file 6. Concurrency - Locks can be used 7. Failure - accessing a site O

Types of Transparency

Openness O The openness of DS is determined primarily by the degree to which new resource-sharing services can be added and be made available for use by a variety of client programs.

Scalability A system is described as scalable if it remains effective when there is a significant increase in the number of resources and the number of users. Challenges: O Controlling the cost of resources or money. O Controlling the performance loss. O

EXAMPLES

Examples of Distributed Systems O Local Area Network and Intranet O Database Management System O Internet/World-Wide Web O Mobile and Ubiquitous Computing

Local Area Network and Intranet

Database Management Systems

Internet intranet % % ISP % % backbone satellite link desktop computer: server: network link:

World Wide Web

Mobile & Ubiquitous Computing Internet Host intranet Printer Wireless LAN GSM/GPRS gateway Mobile phone Laptop Host site Camera Home intranet