Files System

Files System

1. Levels

   • O. S.
     • Gestión
   • User
     • Access

2. Files (bytes having meaning only to the creator)

   • it is an entry in a directory
     • Open
       • Sequential accsess
       • Direct access
   • Attributes (Name, date)
   • Structure
     • None
       • interprets for O. S. or Programs
         • algorithmic pieces
           • Application Programs
             • Logical File System
               • File-organization Module
                 • Basic File System
                   • IO Control
                     • Devices
     • Simple
     • Complex

3. Issues

   • Blocking
     • User or O. S.
       • must pack bytes into a physical block
   • Mounting
   • Sharing

4. Iplementation

   • Virtual Files System (VFS)
     • Provide an object oriented
     • API (interface)
   • Free Space Management
     • BIT VECTOR METHOD
     • FREE LIST METHOD
     • GROUPING METHOD
     • COUNTING METHOD
   • Directory Management
     • GAINING CONSISTENCY
   • Efficiency and Performance
     • THE DISK CACHE MECHANISM

5. Allocation Methods

   • CONTIGUOUS ALLOCATION
     • first block location
   • LINKED ALLOCATION
     • file is a linked list of disk blocks
   • INDEXED ALLOCATION
     • • Each file uses an index block on disk to contain addresses of other disk blocks used by the file.
   • UNIX METHOD:
     • technique based on the size of the file

6. DISTRIBUTED FILE SYSTEMS

   • OVERVIEW
   • THE MOUNT PROTOCOL
   • THE NFS PROTOCOL
   • NFS ARCHITECTURE
   • PATH-NAME TRANSLATION
   • CACHES OF REMOTE DATA