1. © Oxford University Press 2011 DISTRIBUTED COMPUTING Sunita Mahajan Sunita Mahajan, Principal, Institute of Computer Science, MET League of Colleges, Mumbai Seema Shah Seema Shah, Principal, Vidyalankar Institute of Technology, Mumbai University

2. © Oxford University Press 2011 Chapter - 8 Distributed File System

3. © Oxford University Press 2011 Topics Introduction to DFS File models Distributed file system design Semantics of file sharing DFS implementation File caching in DFS Replication in DFS Case study

4. © Oxford University Press 2011 Introduction To DFS

5. © Oxford University Press 2011 Functions of DFS Permanent storage Remote information sharing User mobility Availability Diskless workstation

6. © Oxford University Press 2011 Components of DFS Storage service True file service Name service File service v/s file server

7. © Oxford University Press 2011 Desirable features of a good DFS Transparency User mobility Performance Simplicity Ease of use Scalability Availability Reliability Data integrity Security Support for heterogeneous systems

8. © Oxford University Press 2011 File Models

9. © Oxford University Press 2011 Classification of file models Based on file structure and how they can be modified

10. © Oxford University Press 2011 Distributed File System Design

11. © Oxford University Press 2011 Components of DFS True file service – Operations on individual files Directory service – Creating and managing directories

12. © Oxford University Press 2011 Types of File service interface

13. © Oxford University Press 2011 Remote access model NFS and Locus

14. © Oxford University Press 2011 Data caching model/Upload download model

15. © Oxford University Press 2011 Unit of data access transfer File level transfer Block level transfer Byte level transfer Record level transfer

16. © Oxford University Press 2011 Comparison

17. © Oxford University Press 2011 Directory server interface

18. © Oxford University Press 2011 Directory structure

19. © Oxford University Press 2011 Directory view

20. © Oxford University Press 2011 Naming Transparency Server 1Serve / Root Server 1Server 2Server 3Server 4 Dir 1 Dir 4 Y Dir 1 Dir 4 Y Fig 8.8 Naming Transparency

21. © Oxford University Press 2011 Directory naming approaches

22. © Oxford University Press 2011 Semantics Of File Sharing

23. © Oxford University Press 2011 File sharing

24. © Oxford University Press 2011 Types of file sharing semantics

25. © Oxford University Press 2011 Comparison

26. © Oxford University Press 2011 DFS Implementation

27. © Oxford University Press 2011 Methods of DFS lookup

28. © Oxford University Press 2011 Lookup methods

29. © Oxford University Press 2011 Stateful vs stateless servers

30. © Oxford University Press 2011 File Caching In DFS

31. © Oxford University Press 2011 File caching locations

32. © Oxford University Press 2011 Caching techniques-1

33. © Oxford University Press 2011 Caching techniques-2

34. © Oxford University Press 2011 Comparison of caching policies

35. © Oxford University Press 2011 Cache consistency

36. © Oxford University Press 2011 Comparison of Cache consistency algorithms

37. © Oxford University Press 2011 Replication In DFS

38. © Oxford University Press 2011 Replica creation

39. © Oxford University Press 2011 Update protocols Primary copy algorithm Voting algorithm

40. © Oxford University Press 2011 Case Study

41. © Oxford University Press 2011 Network File System architecture

42. © Oxford University Press 2011 NFS: caching

43. © Oxford University Press 2011 Google File system

44. © Oxford University Press 2011 Summary Introduction to DFS File models Distributed file system design Semantics of file sharing DFS implementation File caching in DFS Replication in DFS Case study