1. A method for upgrading a system that includes a first set of agents for collecting target data from a plurality of targets and sending the target data to a first management server, the method comprising: pre-deploying a second set of agents on a set of one or more hosts that are executing the first set of agents; wherein each pre-deployed agent in the second set of agents is configured to, upon activation, collect target data from a respective target of the plurality of targets and send the target data to a second management server; wherein each pre-deployed agent in the second set of agents remains inactive until activation; wherein a respective agent from the first set of agents collects the target data and sends the target data to the first management server while the pre-deployed agent remains inactive; activating a first batch of one or more agents from the second set of agents; wherein each activated agent in the batch of one or more agents begins collecting data from the respective target of the plurality of targets and sending the target data to the second management server; wherein a second batch of one or more agents from the second set of agents remains inactive after the first batch is activated; wherein for each agent in the second batch of one or more agents, the respective agent from the first set of agents continues to collect the target data and send the target data to the first management server; wherein the method is performed by one or more computing devices.