My understanding is that the cyl/head/track info the operating system gets is... pretty far abstracted from reality by the disk firmware, making that difficult to do in any but a very rough way. By 'very rough' I mean that in the normal case, what the OS sees as sequential sectors are sequential on disk, modulo the bad block remapping... but, from what I understand, going further, e.g. Is sector 5557 closer to 6669 or 3331? is all but impossible to answer from the OS. I mean, most of the time we assume that 6669 is closer as the difference between 6669 and 5557 is smaller than the difference between 3331 and 5557, but because the slow part of the disk is usually the rotation and not the head seek, this is not always or even usually the case.

Especially once you start using hardware RAID controllers, the physical overhead of running I/O commands is pretty abstracted away from the kernel.