Data transfer control system for virtual machine system

Abstract

A virtual machine system includes a storage for storing at least transfer priorities of virtual machines, a queuing part for making a queue of data transfer requests which request data transfers between a main storage and an external storage and are received from operating systems which operate on each of the virtual machines, a limiting part for limiting a transfer data length of one data transfer which is requested by each data transfer request in the queue of the queuing part depending on the transfer priority of the virtual machine from which the data transfer request is received, so that a data transfer is made in divisions if the requested transfer data length exceeds a length limit determined by the transfer priority, a generating part for generating a first data transfer request in place of each operating system with the transfer data length determined by the limiting part so as to start a first data transfer between the main and external storages, and a calculating part for calculating a data length of a remaining transfer data which remains to be transferred when the first data transfer is completed and for automatically generating a second data transfer request requesting transfer of the remaining transfer data. The second data transfer request is inserted in the queue of the queuing part so that the remaining transfer data is transferred between the main and external storages in one or a plurality of second data transfers.