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 1 st Generation: Centralized Operating System 2 nd Generation: Network Operating System 3 rd Generation: Distributed Operating System 4 th 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.software engineering database In object-oriented programming, transparency is facilitated through the use of interfaces that hide actual implementations through different classes.object-oriented programminginterfacesclasses

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_(c omputing)

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