1. A system for controlling resources comprising: a control pattern generation unit that generates a plurality of control patterns from virtual system model(s), produced by modeling the behaviors of network element(s) and server(s) of virtual system(s) operating on virtual datacenter(s), and from a resource allocation change policy stipulating a policy or policies of change of allocation of resources to the virtual system(s), the plurality of control patterns proving candidates for control commands to network resources and server resources of the virtual system(s), wherein the control pattern generation unit includes: a prediction equation generation unit that generates, for each of the network element(s) and the server(s) of the virtual system(s), operating on the virtual datacenter(s), an equation of prediction for predicting the processing time for the case of having changed the resources allocated based on the quantity of resources already allocated and on the results of measurement of processing time for the case of using the quantity of resources already allocated; a virtual system model generation unit that generates the virtual system model(s) using the construction information of the virtual system(s) operating on the virtual datacenter(s) and also using the equation of prediction generated by the prediction equation generation unit; and a control pattern derivation unit that synthesizes a configuration included in the virtual system model(s) generated by the virtual system model generation unit and the resource allocation change policy applicable together so as to form the control pattern; and a control unit that carries out prediction of a service level, with the use of the plurality of control patterns, selecting, with the use of the result of prediction, such control pattern that satisfies the service level of the virtual system(s) and that also satisfies a preset standard or reference for selection, from among the plurality of control patterns, and putting the selected control pattern to use, wherein the control unit includes: a simulation execution unit that exercises simulation of predicting a service level using the plurality of the control patterns; a control pattern evaluation unit that selects, based on the result of the simulation, such control pattern that satisfies the service level of the virtual system as well as the preset standard or reference; and a control pattern applying unit that changes an allocation of the network resources and the server resources in accordance with the selected control pattern.