File System Structure

The file system provides the users efficient access to the disk by allowing convenient storage, location, and retrieval of data. 

The Operating Systems use the layering method for every task including file systems, and every layer is responsible for some activities.

The layers are as follows:

1. Application program
2. Logical File System
3. File Organization Module
4. Basic File System
5. I\O Control
6. Devices

Application of each layer: 

1. The application program requests for a file, the request is sent to the logical file system. 

1. The logical file system stores the meta data of the file and the directory structure. If the application program does not have the required permissions, then the logical file system shows an error. It is also responsible for verifying the path to the file.

1. Files are stored in the hard disks from where it is to be retrieved. The files are divided into logical blocks. To store and retrieve data from the file, the logical blocks need to be mapped to the physical blocks. This mapping is done by the file organization module. It also looks over space management. The file organization module decided which physical block is to be allocated to the applications.

1. Once the decision is made, it passes the information to the basic file system. The basic file system issues a command to the I\O Control to fetch the blocks.

1. The I\O control handles any interrupts and contains the device drivers to access the hard disk.

Reference

File System Structure