File Systems
Chapter 6
6.1 Files
6.2 Directories
6.3 File system implementation
6.4 Example file systems
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File Systems - Applied Operating System - Lecture Slides, Slides of Computer Science
These are the Lecture Slides of Applied Operating System which includes Swapping, Virtual Memory, Page Replacement Algorithms, Modeling Page Replacement Algorithms, Design Issues for Paging Systems, Implementation Issues, Segmentation etc. Key important points are: File Systems, Directories, File System Implementation, Example File Systems, Long-Term Information Storage, File Structure, Kinds of Files, Byte Sequence, Record Sequence, Executable File
Typology: Slides
2012/2013
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File Systems
Chapter 6
6.1 Files 6.2 Directories 6.3 File system implementation 6.4 Example file systems
Long-term Information Storage
1. Must store large amounts of data
2. Information stored must survive the
termination of the process using it
3. Multiple processes must be able to access
the information concurrently
File Types
(a) An executable file (b) An archive
File Access
- Sequential access
- read all bytes/records from the beginning
- cannot jump around, could rewind or back up
- convenient when medium was mag tape
- Random access
- bytes/records read in any order
- essential for data base systems
- read can be …
- move file marker (seek), then read or …
- read and then move file marker
Memory-Mapped Files
(a) Segmented process before mapping files
into its address space
(b) Process after mapping
existing file abc into one segment creating new segment for xyz
Directories
Single-Level Directory Systems
- A single level directory system
- contains 4 files
- owned by 3 different people, A, B, and C
Hierarchical Directory Systems
A hierarchical directory system
Directory Operations
1. Create
2. Delete
3. Opendir
4. Closedir
5. Readdir
6. Rename
7. Link
8. Unlink
Implementing Files (2)
Storing a file as a linked list of disk blocks
Implementing Directories (1)
(a) A simple directory
fixed size entries disk addresses and attributes in directory entry
(b) Directory in which each entry just refers to an i-node
Shared Files (2)
(a) Situation prior to linking
(b) After the link is created
(c)After the original owner removes the file
Disk Space Management (2)
(a) Storing the free list on a linked list (b) A bit map
File System Reliability (1)
- A file system to be dumped
- squares are directories, circles are files
- shaded items, modified since last dump
- each directory & file labeled by i-node number File that has not changed
File System Reliability (3)
- File system states (a) consistent (b) missing block (c) duplicate block in free list (d) duplicate data block