Track Replica—The Strategy for Disk Seeking Optimization in Retrieving Multimedia Data

Because of mechanical operations such as head seeking and rotating, disk device based storage is a main bottleneck of a multimedia server. People can make full use of disk rotation time with track-aligned request service. So disk seeking is the main waste in disk I/O. Since multimedia data is almost read-only, the density of magnetic media is increased at speed of 60% per year. In this paper a new strategy to tradeoff between space and disk seeking is provided: cylinder replication is provided. The main work of the paper is: first, present the placement of n-way cylinder replica in single disk and n-d-way cylinder replica in disk array; then the expressions of mathematic expectation of mean seeking distance of the two cylinder replica placement strategies are derived; finally, lots of simulations are carried out. The simulation results not only show that the expressions are correct, but also tell us that cylinder replica strategy works more better than the traditional tradeoffs such as n-way striping and D-way disk mirror.