1. A method of evaluating a benefit of a proposed migration of a first virtual machine (VM) from a source system to a destination system, the method comprising: determining a first amount of a resource of a first type on the source system; determining a second amount of the first resource type on the destination system; determining a third amount of the first resource type to which the first VM is entitled; determining a first resource type cost-benefit metric as a function of the first, second, and third amounts of first resource type; evaluating the benefit of the proposed migration of the first VM as a function of the first resource type cost-benefit metric, wherein the first resource type cost-benefit metric is based on a migration cost and a migration benefit, the migration cost being indicative of negative gain from the migration, while the migration benefit is indicative of positive gain from the migration; determining a migration time necessary to migrate the first VM from the source system to the destination system; and determining the first resource type cost-benefit metric as a function of the determined migration time.