I/O Time: Doing the Math

Now that we have an abstract model of the disk, we can use a little analysis to better understand disk performance. In particular, we can now represent I/O time as the sum of three major components:

$$T_{I/O}=T_{seek}+T_{rotation}+T_{transfer}$$

Note that the rate of I/O ($R_{I/O}$), which is often more easily used for comparison between drives (as we will do below), is easily computed from the time. Simply divide the size of the transfer by the time it took:

$$R_{I/O}=\frac{Size_{Transfer}}{T_{I/O}}$$ ...