As well, smaller sectors mean that there are more gaps per track, and thus less room for useful storage on the device. Often sectors are grouped into clusters , which are sets of contiguous sectors. An advantage of clustering is that at least some sectors of a multi-sector file will be contiguous. This reduces seeking at cost of some increase in wasted space. Notice that the cluster size is one sector.
Rotational delays depend on the speed of revolution.
The transfer time for a track is simply the rotation time. Assume we have just one surface. The previous example assumed sectors of the file were adjacent. Now suppose we have a cluster size of 4 sectors. Averages tend to be approximate.