Write a short note on disk scheduling

One of the responsibities of operating system O/S is to use the hardware efficiently. Whenever a process requires I/O to or from the disc it issues a system call to the operating system. The request state severer pieces of information:

• Whether this operation is input or output
• What the disk address for the transfer is
• What the memory address for the transfer is
• What the number of bytes to be transferred is

                 If the disk controller and drive are available the request can be serviced immediately. If the controller or drive is busy any new request for service will be placed on the queue of pending request for that drive. For a multiprogramming system with several processes the disk queue may often have several pending requests. Therefore when request is accomplish the operating system chooses which pending request to service next.