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Understood by le system device directory symbolic link

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Unformatted text preview: SSD is typically more energy efficient than a hard drive     31 May 2012 1 ­2 wabs to power an SSD ~10 wabs to power a high performance hard drive –  (can also buy a 1 wab lower ­performance drive) Disks and File Systems 23 University of Washington Interface Layers Interface Layers Std. Runtime Library App. Code OS Device-type Dependent Commands Procedure Calls Whatever… 31 May 2012 Disk Syscalls Disks and File Systems 24 University of Washington Exported Abstractions Exported Abstrac<ons App. Code Std. Runtime Library OS Disk Whatever OS + a tiny bit of file type / structure Directories, Directory Entries, Files,… Array of Blocks / .xls 31 May 2012 / root etc Disks and File Systems root etc 25 University of Washington Primary Roles of of the S (file system) Primary Roles the O OS (file system) 1. Hide hardware specific interface 2. Allocate disk blocks 3. Check permissions 4. Understand directory file structure 5. Maintain metadata 6. Performance 7. Flexibility Disk OS Why does the OS define directories? Why not leave that to the library/application layer? / root etc (Why would you want to leave it to the app/library?) 31 May 2012 Disks and File Systems 26 University of Washington File systems   The concept of a file system is simple   the implementaKon of the abstracKon for secondary storage abstracKon = files   lo...
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