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Modulo I Introdução aos Sistemas Distribuídos

This course provides an introduction to distributed systems, covering topics such as hardware, client-server paradigm, networking, and client-server communication. It explores the motivations behind distributed systems and discusses scalability, transparency, multitiered architectures, and types of distributed operating systems.

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Modulo I Introdução aos Sistemas Distribuídos

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  1. Modulo I Introdução aos Sistemas Distribuídos Prof. Ismael H F Santos Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 1

  2. Bibliografia • Sistemas Distribuídos • Santos,F., H., Ismael; Notas de Aula, 2005 • Sistemas Operacionais e Programação Concorrente • Toscani e outros, Editora sagra-luzzatto • Fundamentos de Sistemas Operacionais • Silberschatz, Abraham, Galvin, Peter, Gagne, G., LTC • Sistemas Distribuídos • Andrew S. Tanenbaun; Prentice Hall • Operating System Concepts: Internals and Design Principles • Williiam Stallings, Prentice Hall Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 2

  3. Ementa • Distributed Systems • Hardware for Distibuted Systems • Client Server Paradigm • Networking • Client Server Communication Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 3

  4. SOA Distributed Systems Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 4

  5. Motivation • Distributed system is collection of loosely coupled processors interconnected by a communications network • Processors called nodes, computers, machines, hosts • Site is location of the processor • Reasons for distributed systems • Resource sharing • sharing and printing files at remote sites • processing information in a distributed database • using remote specialized hardware devices • Computation speedup – load sharing • Reliability – detect and recover from site failure, function transfer, reintegrate failed site • Communication – message passing Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 5

  6. A Distributed System Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 6

  7. Definition of a Distributed System (2) • A distributed system organized as middleware. • Note that the middleware layer extends over multiple machines. 1.1 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 7

  8. Transparency in a Distributed System Different forms of transparency in a distributed system. Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 8

  9. Multitiered Architectures (1) • Alternative client-server organizations (a) – (e). 1-29 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 9

  10. Multitiered Architectures (2) • An example of a server acting as a client. 1-30 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 10

  11. Scalability Problems Examples of scalability limitations. Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 11

  12. Scaling Techniques (1) 1.4 The difference between letting: • a server or • a client check forms as they are being filled Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 12

  13. Scaling Techniques (2) 1.5 An example of dividing the DNS name space into zones. Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 13

  14. Types of Distributed Operating Systems • Network Operating Systems • Distributed Operating Systems Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 14

  15. Network-Operating Systems • Users are aware of multiplicity of machines. Access to resources of various machines is done explicitly by: • Remote logging into the appropriate remote machine (telnet, ssh) • Transferring data from remote machines to local machines, via the File Transfer Protocol (FTP) mechanism Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 15

  16. Distributed-Operating Systems • Users not aware of multiplicity of machines • Access to remote resources similar to access to local resources • Data Migration – transfer data by transferring entire file, or transferring only those portions of the file necessary for the immediate task • Computation Migration – transfer the computation, rather than the data, across the system Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 16

  17. Distributed-Operating Systems (Cont.) • Process Migration – execute an entire process, or parts of it, at different sites • Load balancing – distribute processes across network to even the workload • Computation speedup – subprocesses can run concurrently on different sites • Hardware preference – process execution may require specialized processor • Software preference – required software may be available at only a particular site • Data access – run process remotely, rather than transfer all data locally Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 17

  18. Network Structure • Local-Area Network (LAN) – designed to cover small geographical area. • Multiaccess bus, ring, or star network • Speed  10 megabits/second, or higher • Broadcast is fast and cheap • Nodes: • usually workstations and/or personal computers • a few (usually one or two) mainframes Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 18

  19. Depiction of typical LAN Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 19

  20. Network Types (Cont.) • Wide-Area Network (WAN) – links geographically separated sites • Point-to-point connections over long-haul lines (often leased from a phone company) • Speed  100 kilobits/second • Broadcast usually requires multiple messages • Nodes: • usually a high percentage of mainframes Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 20

  21. Communication Processors in a Wide-Area Network Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 21

  22. SOA Hardware Concepts Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 22

  23. Hardware Concepts 1.6 Different basic organizations and memories in distributed computer systems Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 23

  24. Multiprocessors • A bus-based multiprocessor • A crossbar switch • An omega switching network Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 24

  25. Homogeneous Multicomputer Systems • Grid • Hypercube 1-9 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 25

  26. Software Concepts • DOS (Distributed Operating Systems) • NOS (Network Operating Systems) • Middleware Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 26

  27. Uniprocessor Operating Systems • Separating applications from operating system code through a microkernel. 1.11 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 27

  28. Multicomputer Operating Systems • General structure of a distributed system as middleware. 1-22 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 28

  29. Multicomputer Operating Systems (2) • Alternatives for blocking and buffering in message passing. 1.15 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 29

  30. Multicomputer Operating Systems • Relation between blocking, buffering, and reliable communications. Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 30

  31. Distributed Shared Memory Systems • Pages of address space distributed among four machines • Situation after CPU 1 references page 10 • Situation if page 10 is read only and replication is used Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 31

  32. Distributed Shared Memory Systems (2) • False sharing of a page between two independent processes. 1.18 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 32

  33. Network Operating System (1) • General structure of a network operating system. 1-19 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 33

  34. Network Operating System (2) • Two clients and a server in a network operating system. 1-20 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 34

  35. Network Operating System (3) • Different clients may mount the servers in different places. 1.21 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 35

  36. Positioning Middleware • General structure of a distributed system as middleware. 1-22 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 36

  37. Middleware and Openness • In an open middleware-based distributed system, the protocols used by each middleware layer should be the same, as well as the interfaces they offer to applications. 1.23 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 37

  38. Comparison between Systems • A comparison between multiprocessor operating systems, multicomputer operating systems, network operating systems, and middleware based distributed systems. Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 38

  39. Processing Level • The general organization of an Internet search engine into three different layers 1-28 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 39

  40. Multitiered Architectures (1) • Alternative client-server organizations (a) – (e). 1-29 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 40

  41. Multitiered Architectures (2) • An example of a server acting as a client. 1-30 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 41

  42. Modern Architectures • An example of horizontal distribution of a Web service. 1-31 Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 42

  43. SOA Client-Server Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 43

  44. Software and hardware service layers in distributed systems Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 44

  45. Clients invoke individual servers Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 45

  46. A service provided by multiple servers Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 46

  47. Web proxy server Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 47

  48. A distributed application based on peer processes Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 48

  49. Web applets Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 49

  50. Compute server Network computer or PC Application network Thin Process Client Thin clients and compute servers Prof. Ismael H. F. Santos - ismael@tecgraf.puc-rio.br 50

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