File System Implementation

File System Implementation

1. Tecnológico de Costa Rica, Carrera: Ingeniería en Computación, Sede: Cartago, Curso: Principios de sistemas operativos, Profesor: Esteban Arias Méndez, Estudiante: Jason David Espinoza Siles, Carné: 201223941, II semestre, 2016, Libro: File System Implementation capítulo # 12

2. File-System Structure

   • File structure  Logical storage unit  Collection of related information  File system resides on secondary storage (disks)  Provided user interface to storage, mapping logical to physical  Provides efficient and convenient access to disk by allowing data to be stored, located retrieved easily  Disk provides in-place rewrite and random access  I/O transfers performed in blocks of sectors (usually 512 bytes)  File control block – storage structure consisting of information about a file  Device driver controls the physical device  File system organized into layers

3. File System Layers

   • Device drivers manage I/O devices at the I/O control layer  Given commands like “read drive1, cylinder 72, track 2, sector 10, into memory location 1060” outputs low-level hardware specific commands to hardware controller  Basic file system given command like “retrieve block 123” translates to device driver  Also manages memory buffers and caches (allocation, freeing, replacement)  Buffers hold data in transit  Caches hold frequently used data  File organization module understands files, logical address, and physical blocks  Translates logical block # to physical block #  Manages free space, disk allocation

4. Partitions and Mounting

   • Partition can be a volume containing a file system (“cooked”) or raw – just a sequence of blocks with no file system  Boot block can point to boot volume or boot loader set of blocks that contain enough code to know how to load the kernel from the file system  Or a boot management program for multi-os booting  Root partition contains the OS, other partitions can hold other Oses, other file systems, or be raw  Mounted at boot time  Other partitions can mount automatically or manually  At mount time, file system consistency checked  Is all metadata correct?  If not, fix it, try again  If yes, add to mount table, allow access

5. Allocation Methods

   • Linked
   • Indexed
   • Mapping

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