Database DBMS: Latency Computation for Disk

Accessing (reading or writing) a block of tracks requires three steps, each with an associated delay.
1. The time required by the disk controller to position the head assembly on the cylinder of the track where the disk block is located, that is, the seek time.
2. The disk controller waits for the first sector of the access block to rotate under the head. This time is called rotational latency.
3. When the track controller reads or writes data, the sector where the data is located and the gap between the sectors passes through the magnetic head, and the time at this time is called the transfer time.