Distributed Systems - Chapter 1: Introduction - Thoai Nam

Nội dung text: Distributed Systems - Chapter 1: Introduction - Thoai Nam

1. Distributed Systems Thoai Nam Faculty of Computer Science and Engineering HCMC University of Technology
2. Syllabus Khoái löôïng Taøi lieäu Chöông Noäi dung TS LT (BT) (TH,TN) (TL) tham khaûo 1 Giôùi thieäu Heä phaân boá 2 1, 2 2 Giao tieáp giöõa caùc quaù trình 2 1, 2 3 Dòch vuï File 2 1,2 4 Dòch vuï teân 2 1,2 5 Thôøi gian vaø vaán ñeà ñoàng boä 2 1,2 6 Baûo maät 1 (Self-study) 7 Giaûi thuaät phaân boá 3 (Self-study) 8 Ñònh thôøi bieåu cho chöông 1,2 (Self-study) trình 9 OÂn taäp 3
3. Definition of a Distributed System  What is a distributed system? – Multiple connected CPUs working together – A collection of independent computers that appears to its users as a single coherent system [Tanenbaum] – One in which components located at networked computers communicate and coordinate their actions by only message passing [Coulouris]. Khoa Khoa học và Kỹ thuật Máy tính – ĐHBK TP.HCM
4. Advantages and Disadvantages  Advantages – Communication and resource sharing possible – Economics – price-performance ratio – Reliability, scalability – Potential for incremental growth  Disadvantages – Distribution-aware PLs, OSs and applications – Network connectivity essential – Security and privacy Khoa Khoa học và Kỹ thuật Máy tính – ĐHBK TP.HCM
5. Scalability Problems Concept Example Centralized services A single server for all users Centralized data A single on-line telephone book Doing routing based on complete Centralized algorithms information Examples of scalability limitations Khoa Khoa học và Kỹ thuật Máy tính – ĐHBK TP.HCM
6. Multiprocessors (2) a) A crossbar switch b) An omega switching network 1.8 Khoa Khoa học và Kỹ thuật Máy tính – ĐHBK TP.HCM
7. Distributed Systems Models  Minicomputer model – Each user has local machine – Local processing but can fetch remote data (files, databases)  Workstation model – Processing can also migrate  Client-server Model – User has local workstation – Powerful workstations serve as servers (file, print, DB servers)  Processor pool model – Terminals are Xterms or diskless terminals – Pool of backend processors handle processing Khoa Khoa học và Kỹ thuật Máy tính – ĐHBK TP.HCM
8. Uniprocessor Operating Systems Microkernel architecture . Small kernel . User-level servers implement additional functionality Khoa Khoa học và Kỹ thuật Máy tính – ĐHBK TP.HCM
9. Types of Distributed OSs System Description Main Goal Hide and Tightly-coupled operating system for manage DOS multi-processors and homogeneous hardware multicomputers resources Loosely-coupled operating system for Offer local NOS heterogeneous multicomputers (LAN and services to WAN) remote clients Provide Additional layer atop of NOS Middleware distribution implementing general-purpose services transparency Khoa Khoa học và Kỹ thuật Máy tính – ĐHBK TP.HCM
10. Multicomputer Operating Systems 1.14 Khoa Khoa học và Kỹ thuật Máy tính – ĐHBK TP.HCM
11. Network Operating System (2)  Employs a client-server model – Minimal OS kernel – Additional functionality as user processes 1-20 Khoa Khoa học và Kỹ thuật Máy tính – ĐHBK TP.HCM
12. Comparison between Systems Distributed OS Network Middleware- Item Multiproc. Multicomp. OS based OS Degree of transparency Very High High Low High Same OS on all nodes Yes Yes No No Number of copies of OS 1 N N N Shared Basis for communication Messages Files Model specific memory Global, Global, Resource management Per node Per node central distributed Scalability No Moderately Yes Varies Openness Closed Closed Open Open Khoa Khoa học và Kỹ thuật Máy tính – ĐHBK TP.HCM