1. A system for managing data policies on a virtual machine hosted on a server, the virtual machine being allocated at least one virtual storage component, each virtual storage component having a corresponding storage object hosted on a storage system for storing data of the virtual machine, the system comprising: a manager engine configured for: determining a mapping between the virtual machine hosted on the server and each storage object on the storage system that the virtual machine uses for data storage by: for each storage object, determining high-level storage object information used by the virtual machine to access a virtual storage component corresponding to the storage object, the high-level storage object information mapping the virtual machine to the virtual storage component; for each storage object, determining low-level storage object information used by a storage system to access the storage object which corresponds to the virtual storage component, the low-level storage object information mapping the virtual storage component to the storage object; and for each storage object, combining the high-level and low-level storage object information to determine a mapping relationship between the virtual machine hosted on the server and the storage object on the storage system; producing a mapping graph representing mappings between the virtual machine and each of its storage objects, the mapping graph comprising: a virtual machine node representing the virtual machine; at least one virtual storage node, each virtual storage node representing a virtual storage component and comprising a child node of the virtual machine node; and at least one storage object node, each storage object node representing a storage object and comprising a child node of a virtual storage node; producing graph data describing the mapping graph for the virtual machine; and performing data policy management on the virtual machine by using the graph data to perform at least one data policy on each storage object of the virtual machine.