If you know the media transfer rate, how do you calculate the maximum number of sectors per track from that?
Sectors per track
hard drive
Related Solutions
Almost all modern hard drives report 63 sectors per track, because that's the maximum allowed by the BIOS specs.
This number (along with heads and cylinders) is of course fake and used only for compatibility addressing with very old programs. Internally they use a simple sector number starting from 0 (called LBA mode).
The real sector per track number is not only much larger, but it also varies depending on the distance from the spindle. See, for example, this page from the makers of HDDScan.
Bytes per track depends totally on how the manufacturer laid out the disk internally, which you will not know. All modern disks use LBA (logical block addressing), in which the OS addresses the drive on a sector-by-sector basis, not knowing or caring how or where the sectors are physically located on the platters (nor how many platters there actually are).
Not only that, but the number of sectors per track depends on how far out from the spindle motor you are at the time; it's not a spiral like on a CD. The further from the spindle you are, the more sectors per track (and thus the higher the transfer rate).
The following diagram explains it, but note that the diagram is partially incorrect -- instead of the sectors getting bigger as you go outwards from the spindle, the sectors remain the same size and there are more of them per track the further from the spindle you go (which causes your number of bytes per track, sectors per track, etc to go up).
Since the heads will be over a certain track for only one revolution, and you don't know where on disk you are, you cannot know if the next track will have more or fewer sectors, and therefore your transfer rate will fluctuate.
That said, it will only fluctuate if you are reading directly from disk and not out of cache; modern drives have advanced caching algorithms which will prefetch content it thinks you'll ask for next. As a result, if you were measuring transfer rate, you have no idea if it's coming off the platters or out of cache, making such measurements unrepeatable and totally useless.
In other words, you don't. Period.
Best Answer
Quick answer: you can't. While drive geometry plays a part in the drive's performance it is not the only factor by far.
For one the on board cache of the drive (32MB is increasingly common) will disassociate the rate of the data being read from the disk from the data sent over the bus.