Distributed Operating System
- 1. Prepared by, V.Santhi, Assistant Professor, Department of Computer Applications Bon Secours College for Women, Thanjavur
- 2. Fundamentals What is Distributed System? Single processor, Communication advancement interconnected multiple processors Interconnected multiple processors are basically two types 1. Tightly Coupled Systems 2. Loosely Coupled Systems
- 5. Distributed Computing System A distributed system is a collection of processors interconnected by a communication network in which each processor has its own local memory and other peripherals. Communication between any two processors of the system take place by message passing over the communication network. A distributed system is one in which components located at networked computers communicate and coordinate their actions only by passing messages
- 6. 1945-1950 Loading Machine 1950-1960 Batch Processing 1960 Multiprogramming 1960-1970 Time Sharing Systems Mutics, IBM 360 1969-1973 LAN & WAN ARPA Net, Eternet 1960-Early 1980 MiniComputers PDP, VAX 1980s Workstations Altoe 1980-Present Workstation Server Model Sprite, V System 1990 Clusters BEOWFUL Late 1990 Cloud Computing Globus Evolution of Distributed Computing System
- 7. Distributed Computing System Models Minicomputer model Workstation model Workstation-server model Processor-pool model Cluster model Grid computing
- 9. Extension Centralized Time sharing system Few minicomputers interconnected by a communication network. Multiple users 1. User must log on his/her home minicomputer. 2. Thereafter, he/she can log on a remote machine by telnet. Resource sharing 1. Database 2. High-performance devices Ex: ARPAnet
- 10. Workstation Model(diskful and a local filesystem)
- 11. anSeveral workstations connected by a communication network Workstations equipped with own disk At any one time, other workstations idle, resulting in the waste of CPU time. Workstations are interconnect with high speed LAN Process migration Users first log on his/her personal workstation. If there are idle remote workstations, a heavy job may migrate to one of them
- 12. Issues: How to find am idle workstation How to migrate a job What if a user logs onto a workstation which is running a process of a remote machine (preemptive process migration facility)
- 13. Workstation-Server Model(c-s processes can be on the same m/c )
- 14. Client workstations Diskless Graphic/interactive applications processed in local All file, print, http and even cycle computation requests are sent to servers.
- 15. Server minicomputers Each minicomputer is dedicated to one or more different types of services. Client-Server model of communication RPC (Remote Procedure Call) RMI (Remote Method Invocation)
- 16. A Client process calls a server process’ function. No process migration invoked so the response time is guaranteed ) Example: NSF Advantages (cost,maintenance,anywhere,upgradation)
- 18. Clients: They log in one of terminals (diskless workstations or X terminals) All services are dispatched to servers.
- 19. Servers: Necessary number of processors are allocated to each user from the pool. Better utilization but less interactivity
- 20. Pool of backend processors handle processing –Run server manages the backend processors –User does not log on to his home m/c ( like in other models) –Better utilization of processing power
- 21. Hybrid Model Combine the advantages of both workstation-server and the processor-pool model Guaranteed response time to interactive jobs More expensive to implement
- 22. Why are Distributed Computing Systems Graining Popularity DOS more complex and difficult to build than centralized system. Increased complexity Effectively using &n managing large no of distributed resources. System software of DOS handle communication and security problems very different than centralized Special software needed for loss of messages during transmission Prevent Overloading of the network
- 23. Inherently Distributed Applications Applications are inherently distributed in nature – realization DOS for collecting, preprocessing and accessing the data Ex: Airline reservation Banking system
- 24. Information Sharing among Distributed Users Efficient person – to – person communication facility by sharing information over great distance Information generated by one user efficiently shared by the users.