1. 旋转延迟：
旋转延迟是所需扇区在磁盘驱动器的读写磁头下旋转所需的时间。
换句话说，磁盘被划分为许多环形磁道，这些磁道又被进一步划分为称为扇区的块。所以Rotational Latency是读/写磁头从当前位置旋转到请求扇区所需的时间。
磁盘的平均旋转延迟是磁盘旋转一圈所需时间的一半。
旋转延迟时间取决于磁盘的旋转速度，以每分钟转数 (RPM) 为单位。
2. 中转时间：
将数据从一处传输或移动到另一处所需的时间。它是传输开始和传输完成之间的时间间隔。
它随磁盘的旋转速度而变化，磁盘旋转得越快，读取数据的速度就越快。
它不仅取决于磁盘的旋转速度。但也取决于轨道和扇区密度。密度越大，时间越短。磁盘传输时间还取决于要传输的数据量。
磁盘调度中的旋转延迟和传输时间之间的差异：
| Rotational Latency Time | Transfer Time |
|---|---|
| Rotational Latency is the amount of time it takes for the desired sector of a to rotate under the read-write heads of the disk drive. | The time it takes to transmit or move data from one place to another. It is the time interval between the start of the transfer and the completion of the transfer. |
| Rotational Latency = (Angle between current position and the required sector) / (Rotational frequency). | T = b/rN T is Transfer time, b is number of bytes to be transfered, N is number of bytes on a track and r is rotational speed in Rps |
| Maximum latency = 60/rpm Average latency = 0.5*Latency Time |
It takes about 1 sec to transfer 30-60MB of data |
| It can be reduced if subsequent request belongs to adjacent sector. | It depends on the respective machine. |