Providing Extra-Surfaces to Decrease Write Commit Times in Disk Subsystems
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
This invention decreases commit times of write requests in disk subsystems by providing extra surfaces reserved for write requests. The response time of an I/O request in the disk subsystem consists of several components: (1) waiting time until the device becomes free, (2) waiting time until a path to the device becomes available, (3) seek time of the arm to the specified cylinder, (4) latency time for the angular position of the device to reach the specified sector, (5) Rotational Position Sensing (RPS) delay in order to reconnect to the channel, and (6) the actual data transfer time. There are two types of I/O requests: a read request and a write request. In a non-cached (native) control unit environment, both read and write requests are served in the same manner except for the direction of data movement.