CONTROL SYSTEM FOR MAGNETIC DISK DEVICE

PURPOSE:To improve the throughput of a whole magnetic disk subsystem by minimizing the CCW executing time and also preventing the I/O sinking. CONSTITUTION:The channel side transfer time tc and the DKU side transfer time td are calculated, and the DKUk physical positioning time ts is calculated (step 101-103). The idle state of an external memory 205 is checked, and the reservation state of each transfer path is known when a positioning action ends based on the time ts and a transfer path use reservation table (step 104-105). The data are once stored in the memory 205 and one of the off-line load 108, the through transfer 109 and the fast writing 107 is selected based on the idle state of the transfer path (step 106). Thus, the optimum CCW executing time is secured and the throughput is improved for a whole magnetic disk subsystem.