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Distributed Systems

Distributed Systems. Xining Li Dept. of Computing and Information Science University of Guelph Canada. Chapter 1: Introduction. What is a Distributed system? Why do we need distributed Systems? History of Distributed Systems. Applications of Distributed Systems. Goals and Objectives.

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Distributed Systems

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  1. Distributed Systems Xining Li Dept. of Computing and Information Science University of Guelph Canada Distributed Systems

  2. Chapter 1: Introduction • What is a Distributed system? • Why do we need distributed Systems? • History of Distributed Systems. • Applications of Distributed Systems. • Goals and Objectives. Distributed Systems

  3. Computer processor performance evolution: Distributed Systems

  4. Gordon Moore(1965) Prediction: Distributed Systems

  5. Definition of a Distributed System (Tanenbaum): • A distributed system is: A collection of independent computers that appears to its users as a single coherent system. Distributed Systems

  6. Centralised Systems: • System shared by users all the time • All resources accessible • Software runs in a single process • Single physical location • Single point of control • Single point of failure Distributed Systems

  7. Decentralised Systems: • Multiple autonomous components • Components shared by users • Some resources may not be accessible • Software can run in concurrent processes on different processors • Multiple physical locations • Multiple points of control • Multiple points of failure • No global time • No shared memory (in most cases) Distributed Systems

  8. Applications (Killer): Distributed Systems

  9. Common distributed computing examples • rlogin or telnet (for remote access) • network file system, network printer etc • ATM (cash machine) • Distributed databases • Network computing • Global positioning systems • Retail point-of-sale terminals • Air-traffic control • Enterprise computing • WWW Distributed Systems

  10. SETI: Search for Extraterrestrial Intelligence • To look for aliens • Radio Telescope: Arecibo (305m) • Located in: Puerto Rico • Accept 4,000,000 radio bands • Screen saver to do analysis • UC Berkeley Distributed Systems

  11. Radio Telescope: Arecibo (305m) Puerto Rico Distributed Systems

  12. Distributed.com RC5 • To find the correct solution for RSA Lab’s Secret Keys • Award: $10,000USD • RC_56: 250 days (1997) • RC_64: 1,757 days (2002) • RC_72: ? • Ex: RC_64: 18,446,744,073,709,551,616 keys • 160,000 PC’s are working on this project Distributed Systems

  13. CERN: European Organization for Nuclear Research • CERN is the world's largest particle physics centre. Here physicists come to explore what matter is made of and what forces hold it together. • A new Collider: Large Hadron Collider (2007) • Expected data: 10,000,000GB • Need 20,000,000 CDs to store • Solution: Distributed systems Distributed Systems

  14. Brief History of Distributed Systems: Distributed Systems

  15. Basics of Distributed Systems: • Networked computers (close or loosely coupled) that provide a degree of operation transparency • Distributed Computer System = • independent processors + networking infrastructure • Communication between processes (on the same or different computer) using message passing technologies is the basis of distributed computing Distributed Systems

  16. Goals of Distributed Systems: • Resource sharing: easy for users to access remote resources. • Transparency: to hide the fact that processes and resources are physically distributed across multiple computers. • Openness: to offer services according to standard rules. • Scalability: easy to expand and manage. Distributed Systems

  17. ISO RM-ODP: forms of transparency : Distributed Systems

  18. Scalability Problems: Centralized paradigm Distributed Systems

  19. Scalability Problems: Decentralized paradigm • No machine has complete information about the systems state. • Machines make decisions based only on local information. • Failure of one machine does not ruin the algorithm. • There is no implicit assumption that a global clock exists. Distributed Systems

  20. User Requirements : • What services the system can provide? • How easy to use and manage the system? • What benefits the system can offer? • What is the ratio of performance/cost? • How reliable the system is? • How secure the system can guarantee? Distributed Systems

  21. Distributed Computer System Metrics • Latency – network delay before any data is sent • Bandwidth – maximum channel capacity (analogue communication Hz, digital communication bps) • Granularity – relative size of units of processing required. Distributed systems operate best with coarse grain granularity because of the slow communication compared to processing speed in general • Processor speed – MIPS, FLOPS • Reliability – ability to continue operating correctly for a given time • Fault tolerance – resilience to partial system failure • Security – policy to deal with threats to the communication or processing of data in a system • Administrative/management domains – issues concerning the ownership and access to distributed systems components Distributed Systems

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