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Storage Management - Coggle Diagram

- - - - Exclusive lock
        writer lock which can be acquired by one process at a time
      - Shared lock
        reader lock which can be acquired by several processes concurrently
      - Locking scheme
        
        Advisory
        Software developers to ensure the locks
        
        UNIX systems adopts this scheme
        
        Mandatory
        The operating system ensures locking integrity
        
        Windows operating systems adopt this scheme
        
        In this scheme, deadlock can happen
- - - - Path
        Every file in the system has a pathname.
        
        A user must know the pathname of the file desired.
        
        Absolute Path Name
        Begins at the root
        
        Relative Path Name
        Path from the current directory
      - A special user directory
        OS first searches the local UFD, and if the file is found, it will be used.
        If the file is not found in local UFD, the system searches the special user directory that contains the system files.
        
        Search Path: Sequence of directories searched when a file is named
    - - Current Directory
        Each process has current directory
        
        It contains most of the files that are of current interest to the process.
    - - Traits
        
        Relatively simple to traverse the graph and to determine when there are no more references to a file.
        
        Poorly designed algorithm may cause infinite loop
      - Garbage Collection
        
        traversing the entire file system, marking everything that can be access.
        
        collect everything that is not marked onto a list of free space
      - Shared File/Directory
        Only one actual file exists, so any changes made by one person are immediately visible to other
        
        Link
        A pointer to another file or sub-directory
        
        OS ignores links when traversing directory tree
        
        Symbolic Link
        
        Deletion of a link need not affect the original file; only the link is removed
        
        Links to removed file are keep untouched until an attempt is made to use them
        
        Resolve
        Use the path name to locate the real file
        
        Duplicate Directory
        Make the original and the copy indistinguishable by simply copying all information in original to the copy.
        
        A file may have multiple absolute pathnames.
        
        Deleting the file may leave dangling pointers to the nonexistent file.
        
        Non-symbolic Link (hard link)
        keeping a reference count in the file information block