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File System Implementation

File System Structure File System Implementation Directory Implementation Allocation Methods Free-Space Management Efficiency and Performance Recovery Log-Structured File Systems NFS File-System Structure File structure Logical storage unit Collection of related information File system resides on secondary storage (disks). File system organized into layers. File control block – storage structure consisting of information about a file. Operating System Concepts 12.1 Silberschatz, Galvin and Gagne ©2002 Operating System Concepts 12.2 Silberschatz, Galvin and Gagne ©2002 Layered File System A Typical File Control Block Operating System Concepts 12.3 Silberschatz, Galvin and Gagne ©2002 Operating System Concepts 12.4 Silberschatz, Galvin and Gagne ©2002 In-Memory File System Structures The following figure illustrates the necessary file system structures provided by the operating systems. Figure 12-3(a) refers. | Chapter 12 File System Implementation File-System Structure File System Structure File System Implementation Directory Implementation Allocation Methods Free-Space Management Efficiency and Performance Recovery Log-Structured File Systems NFS File structure Logical storage unit Collection of related information File system resides on secondary storage disks . File system organized into layers. File control block - storage structure consisting of information about a file. Operating System Concepts 12.1 Silberschatz Galvin and Gagne 2002 Operating System Concepts Silberschatz Galvin and Gagne 2002 f Layered File System Operating System Concepts application programs logical file system i fFle-organiiation module I baste file system I O conlrol I devices 12.3 Silberschatz Galvin and Gagne 2002 In-Memory File System Structures The following figure illustrates the necessary file system structures provided by the operating systems. Figure 12-3 a refers to opening a file. Figure 12-3 b refers to reading a file. Operating System Concepts 12.5 Silberschatz Galvin and Gagne 2002 Operating System Concepts A Typical File Control Block Silberschatz Galvin and Gagne 2002 11 Virtual File Systems Schematic View of Virtual File System Virtual File Systems VFS provide an object-oriented way of implementing file systems. VFS allows the same system call interface the API to be used for different types of file systems. The API is to the VFS interface rather than any specific type of file system. Operating System Concepts 12.7 Silberschatz Galvin and Gagne 2002 Directory Implementation Linear list of file names with pointer to the data blocks. simple to program time-consuming to execute Hash Table - linear list with hash data structure. decreases directory search time collisions - situations where two file names hash to the same location fixed size I Allocation Methods An allocation method refers to how disk blocks are allocated for files Contiguous allocation Linked allocation Indexed .