1. SUMAN K REDDY BURJUKINDI

2. 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

3. Definition of DOS A collection of independent computers that appear to the system users as a single computer presenting a transparent view of a multiple computer system with distributed resources and control.[8] Examples – Personal workstations + a pool of processors + single file system. – Robots on the assembly line + Robots in the parts department. – A large bank with hundreds of branch offices all over the world.

4. Goals of DOS Efficiency Robustness Flexibility Consistency

5. Definition of Transparency “Is defined as the concealment from the user and the application programmer of the separation of components in a DS, so that the system is perceived as a whole rather than as a collection of independent components” Coulouris et al It means that any form of Distributed System should hide its distributed nature from its users appearing and functioning as a normal centralized system.[8]

6. Types of Transparency Access transparency: This transparency is used to access the local and the remote host in the same way.[2] Example: NFS

7. Location Transparency: Users of a Distributed System are not aware where a resource is physically located.[1] The resources are referred by logical names. Example: area codes

8. Migration transparency: Resource can be moved to different location without having its name changed and the user should not be aware of the resource location. [5]

9. Relocation transparency: If a resource moves while in use this should not be noticed by the end user.[3]

10. Concurrency Transparency: Multiple users sharing a resource without any interference.[4] It is similar to the time sharing concept.

11. Replication transparency: The system makes multiple copies of files and data without the knowledge of users trying to access the same file or data from different locations. It ensures consistency of multiple instances of files and data.[1]

12. Parallelism transparency: It allows parallel activities without users knowing how, when and where are the activities carried out by the system.[8]

13. Failure transparency: Despite any failures in the system the task needs to be completed successfully. It ensures fault tolerance, graceful performance and minimum damages to the user.

14. Performance Transparency:The variation in load should not lead to performance degradation. This can be achieved by automatic reconfiguration in response to the load changes.[2] It ensures a consistent and predictable performance level.

15. Size transparency: The system can expand in size without the knowledge of the user. It pertains to the incremental growth of the hardware.[1] It is related to modularity and scalability of a system.

16. Persistence transparency: The resource can exist either on a disk or a permanent memory and its existence should not affect the user.[2]

17. Revision transparency: This transparency refers to the vertical growth of the system which refers to the software revisions which are not visible to the users.[3]

18. Security transparency: There needs to be minimum user interference with the cryptographic secure access of resources, the users will otherwise avoid the security in preference to the productivity.[8]

19. Categorization Different transparencies are categorized based on the way they fulfill the system goals. They are as follows:

20. Goal: Efficiency Concurrency Transparency Parallelism Transparency Performance Transparency

21. Goal: Robustness Failure Transparency Replication Transparency Size Transparency Revision Transparency

22. Goal: Flexibility Access Transparency Location Transparency Relocation Transparency Migration Transparency Size Transparency Revision Transparency

23. Goal: Consistency Access Transparency Replication Transparency Performance Transparency Persistence Transparency

24. Active Projects E1 is a distributed operating system project, based on the following concepts: object replication component model support persistence

25. References [1]A. S. Tanenbaum, “Distributed Operating Systems”,Prentice Hall, pp.22-25,2001. [2] Y. Lu, “Distributed Operating Systems”, UNL [3]R. Chow,T. Johnson, “Distributed Operating Systems & Algorithms”, Addison Weley, pp.29-32,1999. [4]J. Wein, “Parallel & Distributed Systems” [5]B. Karp, “RPC & Transparency”,UCL Computer Science,2006

26. References [6] Parallel and Distributed Operating System Group, MIT http://project-iris.net/http://project-iris.net/ [7] IRIS: Infrastructure for Resilient Internet Systems http://project-iris.net/ http://project-iris.net/ [8]http://en.wikipedia.org/wiki/Transparency_(Distribu ted Systems)