Optimum head separation in a disk system with two read/write heads.

We study a mathematical model of computer disk storage devices having two movable read/write heads. Storage addresses are approximated by points in the continuous interval [0,1], and requests for information on the disk are processed first-come- first-served. Our major objective is the equilibrium expected distance, E(d), that the heads are moved in processing a request. For the problem of designing the separation distance, d, we show that E.(0.44657) = 0.16059 = min E(d). Thus, a basic insight of the analysis is that a system with two heads performs more than twice as well as a system with a single head. We compare our results with those for other two-head disk systems.