A method includes assigning each of a plurality of disk write and disk read requests to respective ones of a plurality of queues. Each queue has an occupancy level and a weight. A score is assigned to each of the plurality of queues, based on the occupancy and weight of the respective queue. An operation type is selected to be granted a next disk access. The selection is from the group consisting of disk write, disk read, and processor request. One of the queues is selected based on the score assigned to each queue, if the selected operation type is disk write request or disk read request. The next disk access is granted to the selected operation type and, if the selected operation type is disk write or disk read, to the selected queue.