The invention relates to a multiple QoS file system and methods of processing files at different QoS. The file system allocates VLUNs and using rules chooses an initial QoS for a file when created and moves files to different QoS using rules. Users see a single unified space of files, while administrators place files on storage according to file attributes. A file system enhances the descriptive information for each file to contain the chosen QoS for the file. The invention classifies volumes (e.g., file systems or LUNs) according to application requirements and allocates space for volumes. An IT administrator configures volumes specifying size, type and priority. The host schedules I/O requests in priority queues using the volume definition to match applications and reduce seek time between volumes of different priorities. The data storage system therefore places data on the performance band of a storage device that best supports needs.