Optimal Data Dispatching Methods in Near-Line Tertiary Storage System

Many applications like digital libraries use Near-line Tertiary Storage Systems (TSS) to store their massive data. TSS consists of main memory, disks and tertiary devices. Typically highly referenced or recent data are stored on disks and historical data are stored on tertiary storage devices. We call it Data Dispatching: the determination of what kind of data should be stored on disks and what kind of data should be stored on tertiary storage devices. Traditionally it was up to the Database Management System (DBMS) administrator to dispatch data by hand. But DBMS has to take the responsibility if we want to bring tertiary storage devices under the control of DBMS. We proved in this paper that the data dispatching is an optimal problem and can be reduced to the famous binary knapsack problem. Experimental results showed that the average response time of TSS could be decreased by using optimal data dispatch method.