Abstract: By adjusting the advancement rate of an optical data storage medium in response to the amount of data to be written, and operating a laser with a minimum amount of write laser power level for the particular advancement rate to achieve a desired level of write effectiveness, data signals are written to the optical medium with a minimum amount of power. Where the optical medium comprises an optical disk, choosing the rate of disk rotation selectively establishes the advancement rate. Similarly, where the optical medium comprises an optical tape, choosing the rate of tape advancement from source reel to take-up reel selectively establishes the advancement rate. Preferably, the advancement rate is increased or decreased depending upon whether a greater or lesser quantity or write length of data resides in a write queue.

Abstract: The utilization of a level of a data storage hierarchy is monitored and the data in such level is manipulated in response thereto. In a data storage hierarchy including an automated storage library, the utilization is a mount rate relative to the maximum possible mount rate. When the combined utilization of all of the libraries exceeds a predetermined value, data is promoted from the most utilized library (or libraries) to a higher level in the data storage hierarchy until the combined utilization of all of the libraries is sufficiently reduced. By reducing the combined utilization of all of the libraries, the average queue time for library mount requests is prevented from becoming excessively long relative to the average library mount cycle time.