A storage controller is provided. The storage controller includes a host interface, a drive interface, and a quality of service control module coupled with the host interface and the drive interface. The QoS module includes read and write queues for each data stream, each queue associated with corresponding token buckets, and an arbiter, configured to receive requests from the read and write queues, and to service the read and write queues in an order at least partially determined by a quantity of tokens in each token bucket. The QoS module also includes a quality of service measurement module, configured to measure quality of service levels for each of the read and write queues, and a bandwidth allocation manager, configured to allocate tokens to each token bucket at a rate corresponding to the service level agreements and the measured quality of service level for each of the read and write queues.