A computer implemented method of scheduling a plurality of virtual machines for execution by a physical computing infrastructure is described. The plurality of virtual machines are deployable to a subset of the physical computing infrastructure to execute a computing task. The method includes determining a subset of the infrastructure and a time period for deployment of each virtual machine, so that the virtual machines are scheduled to execute to completion over an aggregate of all time periods. The determination is based on a mathematical optimization of a risk function for each of the plurality virtual machines that corresponds to a relative risk that at least one virtual machine will fail to fully execute its task to completion.