Recent advances in Cable TV networks and multimedia technologies open
the possibilities for network/service/content providers to offer resid
ential customers with video-on-demand services. However, the mass stor
age system in supporting such services demands proper organization and
management. In this paper we present a three-level hierarchical netwo
rk storage architecture for the video-on-demand storage system. At the
first-level (Local Service Center, LSC) a limited number of programs
with high viewing probabilities are stored; while at the second-level
(Local Central Service Center, LCSC) a few programs with second high v
iewing probabilities are stored. The third-level (Central Service Cent
er, CSC) contains all programs provided in the system. Based on this a
rchitecture and the program viewing probability distribution function,
we use a minimum-cost function to find out the numbers of programs st
ored in the two service centers (LSC and LCSC) and numbers of links am
ong these three service centers. We also describe two program realloca
tion algorithms which swap programs between service centers according
To the change in user request patterns.