With the increase in size, complexity, and heterogeneity of grid computing environments, we argue that, in addition to performance metrics, the resource allocation algorithms should be designed for robustness. That is, they should have the ability to maintain performance under a wide variety of operating conditions. Although robustness is easy to define, there are no widely used metrics for this property. We introduce the concept of robustness and present an analysis technique to determine the robustness of a resource allocation. As the main contributions of the paper, we present a mathematical description of a metric for the robustness of a resource allocation with respect to a specific disturbance. Simulation results prove the efficiency and applicability of our algorithms.