Why is rotational latency usually not considered in disk scheduling? How would you modify SSTF, SCAN, and C-SCAN to include latency optimization?

Most disks do not export their rotational position information to the host. Even if they did, the time for this in order to reach the scheduler would be subject to imprecision and the time consumed by the scheduler is variable, so the rotational position in order would become incorrect. Further, the disk requests are usually given in terms of logical block numbers, and the mapping among logical blocks and physical locations is very difficult