Table 1: The symbols used in our mathematical model and derivation.

Radius of the innermost track
Radius of the outermost track
The speed of the read/write head
In C-SCAN, the time to backtrack from the outer to the inner track
Arrival rate of the requests
r.v. denoting radius of the track specified by a memory request
pdf for
r.v. denoting job size; rotational latency + transfer time for a request
pdf for
The (large) number of jobs in a hypothetical request sequence
The average access time of a job
The time access time of label
The part of during which the head is moving
The part of during which the head is processing a job
r.v. denoting the number of jobs in the system not being processed at a random time
The load of the system
r.v. denoting the remaining time on a job being processed
The pdf of the location of the head, given that it is not backtracking