ch11 - Chapter 11: File System Implementation...

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Chapter 11: File System Chapter 11: File System Implementation Implementation Adapted to COP4610 by Robert van Engelen
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11.2 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts – 7 th Edition, Jan 1, 2005 File-System Structure File-System Structure File structure concept: A logical storage unit A collection of related information File system implements file structures File system resides on secondary storage (disks) File system structure is organized into layers Layered file system structure
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11.3 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts – 7 th Edition, Jan 1, 2005 File-System Structure (cont’d) File-System Structure (cont’d) Logical file system - manages meta-data about the file-system structure in file- control blocks File organization module - maintains information about files and translates logical block addresses into physical block addresses Basic file system - issues generic commands to the driver, e.g. read drive1, cylinder 73, track 2, sector 10 Device drivers - lowest level of I/O control with interrupt handlers to transfer data between memory and disk, e.g. read block 123 Layered file system structure
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11.4 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts – 7 th Edition, Jan 1, 2005 File-Control Blocks File-Control Blocks The logical file system maintains structures consisting of information about a file: file-control block (FCB) Typical FCB
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11.5 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts – 7 th Edition, Jan 1, 2005 In-Memory File System Structures In-Memory File System Structures Operations performed when opening a file Operations performed when reading the file after opening
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11.6 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts – 7 th Edition, Jan 1, 2005 Virtual File Systems Virtual File Systems 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 VFS architecture supports different object types, e.g. file objects, directory objects, whole file system The API is to the VFS interface, e.g: open() read() write() mmap()
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11.7 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts – 7 th Edition, Jan 1, 2005 Directory Implementation Directory Implementation How to efficiently implement directory structures?
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11.8 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts – 7 th Edition, Jan 1, 2005 Directory Implementation (cont’d) Directory Implementation (cont’d) Linear list of file names with pointer to the data blocks Simple to program Time-consuming to search for file name in (long) lists Hash Table – linear list with hash data structure Decreases directory search time Collisions – situations where two file names hash to the same location Enlarge the hash table Or use fixed size with overflow chains
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11.9
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This note was uploaded on 10/11/2011 for the course COP 4610 taught by Professor Robertengelen during the Spring '11 term at FSU.

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ch11 - Chapter 11: File System Implementation...

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