1. A method for responding to a request to transfer data between a first virtual machine (VM) in a computer system and a virtual storage device backed up by a data storage unit within a multipath data storage system, the method comprising: identifying the request issued by the first VM, the request being a virtual data transfer request, the first VM being one of a plurality of VMs; identifying a plurality of possible paths over which the data could be routed from the computer system to the data storage system and multipath routing information related to a state of each of the possible paths; determining VM-specific information related to the first VM, wherein the VM-specific information indicates a priority of the first VM relative to other VMs of the plurality of VMs; selecting one path of the plurality of paths according to an algorithm, which takes as inputs at least contents of the multipath routing information and contents of the VM-specific information; and routing a physical data transfer request corresponding to the virtual data transfer request to the data storage system over the one path that was selected.