1. A computer system, comprising: a storage apparatus coupled to a host computer via a network; and a storage management computer configured to access the storage apparatus and the host computer, wherein the storage apparatus comprises a storage unit configured to store data read/written by the host computer and is configured to provide the host computer with a storage area of the storage unit as one or more volumes, wherein the storage management computer comprises a first memory configured to store one or more task information each comprising contents of a respective process performed on the storage apparatus, and a scheduled starting time and a scheduled termination time of the respective process, and wherein the one or more task information include a first task information and a second task information, and when resources used in a process of the second task information are the same as resources used in a process of the first task information, the storage management computer is configured to compute times required for executing the first task information and the second task information, wherein the storage management computer is configured to: acquire contents of a configuration change performed on the storage apparatus; update contents of at least one of the one or more task information stored in the first memory to obtain updated task information, wherein the at least one of the one or more task information is related to the configuration change; compute the times required for executing the processes of the first task information and the second task information by using the updated task information as the first task information; determine that the times required for executing the processes of the first task information and the second task information conflict; determine that at least one of the processes of the first task information and the second task information is not completed by the scheduled termination time in response to determining that the times required for executing the processes of the first task information and the second task information conflict; and switch a task order between the process of the first task information and the process of the second task information and change the scheduled starting time of at least one of the process of the first task information or the process of the second task information so that a time for executing the process of the updated task information as the first task information does not conflict with the time for executing the process of the second task information in response to determining that at least one of the processes of the first task information and the second task information is not completed by the scheduled termination time, wherein the storage apparatus further comprises a second memory configured to store an input/output data amount per unit time, which is the amount of data transmitted from the host computer to the one or more volumes, wherein the storage management computer is further configured to acquire the input/output data amount per unit time from the second memory of the storage apparatus, wherein the storage management computer is further configured to determine whether at least part of the resources used in the processes of the first task information and the second task information are the same, on the basis of information on an object to be subjected to the respective process and information on a resource used for accessing the one or more volumes, wherein the first memory is further configured to store performance information of the storage area, the performance information indicating Input Output Per Second (IOPS) of a certain volume, and wherein the storage management computer is further configured to: compute processing times required for executing contents of the processes of the first task information and the second task information, based on the contents of the processes of the first task information and the second task information, the object to be subjected to the processes of the first task information and the second task information, and the performance information of the storage area, and add to the processing times a time obtained by multiplying the time during which the processes conflict with each other, by a predetermined coefficient, thereby computing the times required for executing the first task information and the second task information.