A data storage system and associated method are provided wherein a policy engine continuously collects qualitative information about a network load to the data storage system in order to dynamically characterize the load and continuously correlates the load characterization to the content of a command queue of transfer requests for writeback commands and host read commands, selectively limiting the content with respect to writeback commands to only those transfer requests for writeback data that are selected on a physical zone basis of a plurality of predefined physical zones of a storage media.