1. A computer-executable method for determining an allocation configuration for allocating virtual machines to physical machines, the method comprising the steps of: determining a predicted peak usage amount of physical resources for each time interval for individual clusters wherein the clusters include a plurality of virtual machines; setting a constraint that ensures that, for individual combinations of a first physical machine, a second physical machine, and a time interval, the total predicted peak usage amount of the physical resource predicted for the first physical machine if the second physical machine stops during the time interval does not exceed the physical resource amount prepared for the first physical machine; and deriving an allocation configuration by calculating, in accordance with the constraint, a solution to an optimization problem for minimizing, as an objective function, the sum total of the physical resource amounts of the plurality of physical machines to which the virtual machines are allocated.