The invention is directed to a primary data storage system for use in a computer network in which a network allows user computers to transfer data to/from the primary data storage system. In one embodiment, the primary data storage system allows an administrator of the computer network to define two or more volumes on the primary data storage system and define quality of service goals for each volume. The primary data storage system operates so as allocate resources within the primary data storage system to the volumes based upon criticality and performance goals specified for each of the volumes.