An approach is provided for predicting system performance. The approach operates by identifying a Queuing Network Model (QNM) corresponding to an information technology (IT) environment that includes a number of servers that perform a plurality of parallel services. The QNM is transformed to a linear model by serializing the parallel services as sequential services. Hardware based service demands are retrieved from the system. Software-based service demands are inferred from the hardware-based service demands. Predicted performance results of the IT environment are calculated based on the hardware-based service demands, the software-based service demands inferred from the hardware-based service demands, and the system transaction rate of the system.