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Transparency

Transparency

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Transparency

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  1. Transparency Wang, Yang ywang39@student.gsu.edu

  2. OUTLINE • Review • Transparencies in DOS • Categorization • Degree of Transparency • Summary • Reference

  3. Review • Evolution of Modern Operating Systems • What is DOS? • Goals of DOS

  4. Evolution of Modern Operating Systems • 1st Generation: Centralized Operating System • 2nd Generation: Network Operating System • 3rd Generation: Distributed Operating System • 4th Generation: Cooperative autonomous System

  5. Definition of DOS • We define a DOS as an integration of system services ,presenting a transparent view of a multiple computer system with distributed resources and control.

  6. Goals of DOS • Efficiency • Flexibility • Consistency • Robustness

  7. OUTLINE • Review • Transparencies in DOS • Categorization • Degree of Transparency • Reference

  8. Definition of Transparency in DOS • Concealment from the user and the application programmer of the separation of components in a distributed system, so that the system is perceived as a whole than rather as a collection of independent components.

  9. Compare • In software engineering, it is also considered good practice to develop or use abstraction layers for database access, so that the same application will work with different databases; here, the abstraction layer allows other parts of the program to access the database transparently. • In object-oriented programming, transparency is facilitated through the use of interfaces that hide actual implementations through different classes.

  10. Access Transparency • The ability to access both local and remote system objects in a uniform way. • Example: NFS

  11. Location Transparency • Name Transparency • Users have no awareness of object locations (physical location) • "The network is the computer"

  12. Migration Transparency • Resources could be free to move from one location to another without having their names changed • Example: Cell phone & BSC, roaming

  13. Example • Communication with your friends…. • Access • Location • Migration • Access location Migration are interrelated

  14. Failure Transparency • Applications should be able to complete their task despite failures occurring in certain parts of the system. • Fault tolerance • Example: backup database

  15. Replication Transparency • The system is free to make additional copies of files and other resources (for purpose of performance and/or reliability), without the users noticing. • Consistency between copies (DNS master ,slave)

  16. Concurrency Transparency • The users will not notice the existence of other users in the system (even if they access the same resources) • Similar to time-sharing system

  17. Performance Transparency • Load variation should not lead to performance degradation. This could be achieved by automatic reconfiguration as response to changes of the load.

  18. Parallelism Transparency • This permits parallel activities without users knowing how, where, and when these activities are carried out by the systems.

  19. Scaling (Size) Transparency • Can expand in scale(incremental growth) without change to system's structure or application algorithms.(Hardware)

  20. Revision Transparency • This refers to the vertical growth of systems as opposed to the horizontal growth as in scalable transparency. Revision of software not visible to users.

  21. Security transparency • Negotiation of cryptographically secure access of resources must require a minimum of user intervention, or users will circumvent the security in preference of productivity.

  22. Persistence Transparency • Hide whether a (software) resource is in memory or on disk.

  23. Relocation transparency • Should a resource move while in use, this should not be noticeable to the end user.

  24. OUTLINE • Review • Transparencies in DOS • Categorization • Degree of Transparencies • Summary • Reference

  25. Goal: Flexibility • Access location migration size revision

  26. Goal: Consistency • Access Replication Performance

  27. Goal: Robustness • failure replication size revision

  28. Goal:Efficiency • Concurrency Parallelism Performance

  29. OUTLINE • Review • Transparencies in DOS • Classification • Degree of Transparencies • Summary • Reference

  30. Degree • Distribution transparency is generally preferable, but not always a good idea: • It is undesirable to hide the location of the printer from its users

  31. Trade-off • Shielding the system-dependent information from the users is basically a trade-off.

  32. OUTLINE • Review • Transparencies in DOS • Classification • Degree of Transparencies • Summary • Reference

  33. Summary What is Transparency? Categorization Trade-off

  34. Some related articles [1] Application-Transparent Fault Tolerance in Distributed Systems, Thomas Becker [2]On the Structuring of Distributed Systems: The argument for mobility, Todd. [3]Name Transparency in very large scale Distributed file systems, Richard G. Guy et al [3]http://en.wikipedia.org/wiki/Transparency_(computing)

  35. Thanks and Apologize • Thank you! • 谢谢! • shukria

  36. References [1]A. S. Tanenbaum, “Distributed Operating Systems”,Prentice Hall, pp.22-25. [2]R. Chow,T. Johnson, “Distributed Operating Systems & Algorithms”, Addison Weley, pp.29-32. [3]J. Wein, “Parallel & Distributed Systems” [4]B. Karp, “RPC & Transparency”,UCL Computer Science,2006 [5]Y. Lu,”Distributed Operating Systems”,UNL [6]J. Holliday,”Distributed Computing”,SCU [7]B. Karp, S. Hailes,”Distributed Systems & Security:An Introduction,UCL Computer Science,2006