1. A disk array controller comprising: a plurality of host directors provided for a plurality of hosts, one for each, and controlling input/output requests issued from the hosts for executing input/output processing to or from disk devices; and a shared memory shared by the host directors and forming a disk cache, wherein, when the host issues a plurality of read commands to the same cache page, said host director starts a plurality of data transfers while occupying the cache page during processing of said plurality of read commands.