ECE344-Lecture22-FileSystems

ECE344-Lecture22-FileSystems - Lecture 22: File Systems...

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1 Lecture 22: File Systems David Lie ECE344 University of Toronto
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2 ECE344: Operating Systems Outline File Systems Overview of file system Disk Basics – File system design – Consistency and crash recovery – Sharing files – Unix file system Disks – Disk scheduling algorithms – Redundancy in storage systems
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3 ECE344: Operating Systems What is a File System? A file system provides an abstraction for storing, organizing and accessing persistent data – Persistant data that survives the termination of the process that created the data – Should survive crashes, reboots, etc… – This data is stored on disks, flash drives , etc. File-system data is organized as objects called files. Need wasy of funding files: – Files have names and are organized as directories – May have search functionality Files are accessed via system calls – Can have concurrent access to the same file by different threads/processes
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4 ECE344: Operating Systems Abstraction: The File System Interface The OS and user programs have different interfaces to file objects OS interface: – The OS consider files as opaque blobs of bits. – The OS is concerned about: • Storing files, ensuring persistence and durability • Enabling retrieval of files when requested by programs • Maintaining metadata about the files
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5 ECE344: Operating Systems Persistence and Durability Persistence means that data stored on the file system survives across reboots: – The opposite is non-persistent or volatiles storage like DRAM. Contents are erased on reboot. Durability means that data stored on the file system survives if
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This document was uploaded on 02/20/2012.

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ECE344-Lecture22-FileSystems - Lecture 22: File Systems...

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