The general answer is, you can't, at least not meaningfully.
The longer answer is, it is very dependent on the hardware and software in question, both the firmware of the drive and the drivers of the operating system. Even if you were dealing with an isolated case - a single drive running on a dedicated real-time system - the results would depend more on the caching algorithm of the drive controller than the drive's own performance.
In practice, very few operating systems ensure real-time performance or measurement (keeping in mind that 'real-time' means bounded time, not necessarily minimum time). In a general-purpose system such as Windows or the Unices, the use of virtual memory essentially makes predictability impossible.