The present invention implements a mechanism to decide when it is beneficial to switch from the current virtual input/output mechanism to a different one. The present invention determines which input/output mechanism each virtual machine should use based on the available input/output resources of the virtual machines (with their respective available input/output adapters), the number of virtual machines running and their input/output needs, and the input/output needs of the virtual machine being considered. The present invention also provides a mechanism for virtual machine to seamlessly switch input/output mechanisms. When beneficial, the standard hot-plug mechanism of the virtual machine and the hypervisor is used to first remove the existing input/output mechanism and then add the new input/output mechanism.