Block Devices :
Block devices are type of file systems that allow the random acces to completely independent, fixed-sized blocks of data.
Ex : hard disks and floppy disks .
- This are typically are used to store the file-systems.
- They provide the main interface to all the disk devices in a system.
- A block represnts the unit with which the kernel performs I/O.
- When a block is read into memory, it is stored in a buffer.
- The request manager is the layer of software that manages the reading and writing of buffer contents to and from a block-device-driver.
- A separate list of requests is kept for each block-device-driver.
- These requests are scheduled according to a C-SCAN algorithm.
- C-SCAN algorothm exploits the order in which requests are inserted in and removed from the lists.
- The requests lists are maintained in sorted order of increasing starting-sector number.
