Machines, systems and methods for managing quality of service in a virtualized computing environment, the method comprising: provisioning one or more active virtual machines (VMs) over one or more hosts in a virtualized computing network, wherein one or more resources are allocated to the active VMs before the active VMs service one or more requests; monitoring information associated with quality of service defined for servicing of the requests; and designating at least an active VM as a shadow VMs, in response to results of the monitoring, wherein at least one resource remains allocated to the shadow VM, while the shadow VM enters a dormant state and no longer services any requests.