Содержание
- 2. CHAPTER 8: DISTRIBUTED FILE SYSTEM Introduction to File System File-System Structure Directory Implementation Allocation Methods Distributed
- 3. FILE-SYSTEM STRUCTURE File structure Logical storage unit Collection of related information File system resides on secondary
- 4. LAYERED FILE SYSTEM
- 5. A TYPICAL FILE CONTROL BLOCK
- 6. VIRTUAL FILE SYSTEMS Virtual File Systems (VFS) provide an object-oriented way of implementing file systems. VFS
- 7. SCHEMATIC VIEW OF VIRTUAL FILE SYSTEM
- 8. DIRECTORY IMPLEMENTATION Linear list of file names with pointer to the data blocks. simple to program
- 9. ALLOCATION METHODS An allocation method refers to how disk blocks are allocated for files: Contiguous allocation
- 10. CONTIGUOUS ALLOCATION Each file occupies a set of contiguous blocks on the disk Simple – only
- 11. CONTIGUOUS ALLOCATION OF DISK SPACE
- 12. EXTENT-BASED SYSTEMS Many newer file systems (I.e. Veritas File System) use a modified contiguous allocation scheme
- 13. LINKED ALLOCATION Each file is a linked list of disk blocks: blocks may be scattered anywhere
- 14. LINKED ALLOCATION
- 15. FILE-ALLOCATION TABLE
- 16. INDEXED ALLOCATION Brings all pointers together into the index block. Logical view. index table
- 17. EXAMPLE OF INDEXED ALLOCATION
- 18. INDEXED ALLOCATION – MAPPING (CONT.) outer-index index table file
- 19. COMBINED SCHEME: UNIX (4K BYTES PER BLOCK)
- 20. LINKED FREE SPACE LIST ON DISK
- 21. DISTRIBUTED FILE SYSTEM
- 22. DISTRIBUTED FILE SYSTEMS A special case of distributed system Allows multi-computer systems to share files Examples:
- 23. DISTRIBUTED FILE SYSTEMS (CONTINUED) One of most common uses of distributed computing Goal: provide common view
- 24. NAMING OF DISTRIBUTED FILES Naming – mapping between logical and physical objects. A transparent DFS hides
- 25. DFS – THREE NAMING SCHEMES Mount remote directories to local directories, giving the appearance of a
- 26. THE SUN NETWORK FILE SYSTEM (NFS) An implementation and a specification of a software system for
- 27. NFS (CONT.) Interconnected workstations viewed as a set of independent machines with independent file systems, which
- 28. NFS (CONT.) NFS is designed to operate in a heterogeneous environment of different machines, operating systems,
- 29. THREE INDEPENDENT FILE SYSTEMS
- 30. MOUNTING IN NFS Mounts Cascading mounts
- 31. NFS MOUNT PROTOCOL Establishes initial logical connection between server and client Mount operation includes name of
- 32. NFS PROTOCOL Provides a set of remote procedure calls for remote file operations. The procedures support
- 33. THREE MAJOR LAYERS OF NFS ARCHITECTURE UNIX file-system interface (based on the open, read, write, and
- 34. SCHEMATIC VIEW OF NFS ARCHITECTURE
- 35. NFS PATH-NAME TRANSLATION Performed by breaking the path into component names and performing a separate NFS
- 36. NFS REMOTE OPERATIONS Nearly one-to-one correspondence between regular UNIX system calls and the NFS protocol RPCs
- 37. ANDREW FILE SYSTEM (AFS) Completely different kind of file system Developed at CMU to support all
- 38. ANDREW FILE SYSTEM (AFS) Stateful Single name space File has the same names everywhere in the
- 39. AFS Need for scaling led to reduction of client-server message traffic. Once a file is cached,
- 40. AFS On file open() If client has received a callback for file, it must fetch new
- 41. DISTRIBUTED FILE SYSTEMS REQUIREMENTS Performance is always an issue Tradeoff between performance and the semantics of
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