Abstract: Storage requests are divided into high-priority requests generally requiring low response time and low-priority requests generally requiring high throughput. The high-priority requests are further divided into several priorities reflecting different classes of service. The low-priority requests are placed on a low-priority request queue where they are executed in a throughput-optimizing order generally different from their arrival order. For each high-priority request, if there are not more than a predetermined number n (e.g., 1) outstanding requests for execution by the disk drive of greater priority, then the request is placed on a high-priority request queue where it is generally executed ahead of requests on the low-priority request queue. If there are more than n such greater-priority requests outstanding, then the high-priority request is placed on the low priority request queue and included in the throughput optimization along with the low-priority requests.

Abstract: A mixed queue method for managing storage requests directed includes a low-priority request queue on which all low-priority requests are placed and where they are subject to throughput optimization by re-ordering. When a high-priority request limit has not been reached, high-priority requests are placed on a high-priority request queue where they are executed in a pre-emptive manner with respect to the queued low-priority requests, thus experiencing reduced access time. When the high-priority request limit has been reached, the high-priority requests are placed on the low-priority request queue, such that the high-priority requests are included in the throughput optimization along with the low-priority requests on the request queue. Starvation of the low-priority requests is avoided, and the overall throughput of the disk drive is maintained at a relatively high level.