1. A computer system, comprising: at least one storage system; a plurality of host computers, each included in different network segments, respectively, and including a processor, memory and an input/output (I/O) device; a management computer which can access the storage system and the host computers, the management computer including a processor, a memory, an I/O device and configuration management information for managing the I/O device included in the host computers; and an execution computer belonging to a same network segment as the management computer, and including a processor, a memory and an I/O device, and configured to provide a virtual computer which can access the storage system; the storage system including a physical disk for storing data and a disk controller for controlling the physical disk, and configured to provide a storage area of the physical disk as at least one logical volume, wherein: the management computer is configured to extract, responsive to an inputted deployment request, a configuration of the I/O device of an existing host computer of the host computers which is a deployment target, based on the configuration management information; the management computer is configured to send a request to the execution computer to create an imitating virtual computer having a configuration which imitates a configuration of the existing host computer which is the deployment target, the request including the extracted configuration of the I/O device of the existing host computer which is the deployment target; the execution computer is configured to create the imitating virtual computer having an I/O device which matches the I/O device of the existing host computer which is the deployment target, responsive to a received request from the management computer to generate the imitating virtual computer; the management computer is configured to define a first connection authorizing access between a first logical volume provided by the storage system and the created said imitating virtual computer; the management computer is configured to deploy on the imitating virtual computer, a disk image including information on a driver storage path that stores a driver needed by the existing host computer which is the deployment target, to duplicate the disk image into the first logical volume connected to the imitating virtual computer; the management computer is configured to set identification information including an identifier of the existing host computer which is the deployment target, in the imitating virtual computer on which the disk image is deployed, to store the identification information in the first logical volume connected to the imitating virtual computer; the management computer is configured to extract, from the configuration management information, a driver type corresponding to the I/O device of the existing host computer which is the deployment target; the management computer is configured to store the driver corresponding to the extracted driver type in the driver storage path of the disk image duplicated into the first logical volume; the management computer is configured to then deactivate the imitating virtual computer; the management computer is configured to then release the first connection authorizing access between the first logical volume and the imitating virtual computer; and the management computer is configured to then define a second connection authorizing access between the existing host computer which is the deployment target and the first logical volume, whereby a program stored in the logical volume is deployed on the existing host computer which is the deployment target; wherein each host computer is authorized to access one or more logical volume provided only in a same network segment as said each host computer, and wherein the management computer defining the second connection authorizing access between the existing host computer which is the deployment target and the first logical volume, effects the first logical volume into the same network segment as said existing host computer.