1. A method for real-time balancing of workload across a plurality of physical storage systems, comprising: (a) collecting performance data for each of the plurality of physical storage systems, wherein each physical storage system shares access to a plurality of storage devices; (b) computing a set of overall metrics for each of the plurality of physical storage systems, wherein the set of overall metrics for each physical storage system are calculated over a moving window of time to obtain average values; (c) determining if any of the physical storage systems exceeds one or more predefined thresholds; (d) looping back to step (a), in response to determining that none of the physical storage systems are exceeding any of the one or more thresholds; (e) selecting a virtual storage system for migration from one of the plurality of physical storage systems to a destination storage system in response to determining that at least one of the physical storage systems exceeds one or more predefined thresholds, by (i) creating a usage table for each virtual storage system associated with each source physical storage system, wherein creating the usage table further comprises calculating a vfiler ratio (VR), wherein the vfiler ratio is equal to vfiler operations per second divided by physical storage system operations per second, (ii) selecting a source physical storage system and a destination physical storage system, and (iii) selecting the virtual storage system for migration; and (f) migrating the virtual storage system to the destination storage system, wherein the virtual storage system is accessed directly on the destination storage system using network resources assigned to the virtual storage system prior to migrating.