Method and System for Enhanced Scheduling of Memory Access Requests

Abstract

The forgoing objects are achieved as is now described. In information storage systems in which data retrieval requires movement of at least one physical element, a measurable amount of energy and time are required to reposition that physical element in response to each data write or read request. After selecting one or more data requests for dispatch based solely on an approaching or past due time deadline, additional requests are identified for data to be read or written to locations which are in close proximity to previously scheduled requests, obviating the need to expend the full amount of energy and time required to accelerate the physical element and then decelerate the physical element to position it over the desired area within the information storage system. In this manner, data may be transferred to or retrieved from an information storage system more efficiently with less expenditure of energy and time.

1 . An information storage system scheduler for scheduling information storage system access requests, each of said information storage system access request having an associated storage system address associated therewith, said scheduler comprising:
 means for associating a time deadline with selected ones of said plurality of information storage system access requests;   means for periodically selecting one or more of said plurality of information storage system access requests for execution based solely upon an associated time deadline;   means for determining if said associated time deadline for said one or more of said plurality of information storage system access requests can be met while executing at least one additional information storage system access request and said selected one or more of said plurality of information storage access requests; and   means for selecting at least one additional information storage system access request for execution without regard to its associated time deadline based solely upon close proximity between an information storage system address of said at least one additional information storage system access request and either an information storage system address of said selected one or more of said plurality of information storage system access requests, or a current information storage system address if said associated time deadline can be met.   
   
   
       2 . The information storage system scheduler according to  claim 1 , further including a disk storage system having data stored therein within concentric cylinders associated with said information storage system scheduler. 
   
   
       3 . The information storage system scheduler according to  claim 2 , wherein said means for selecting at least one additional information storage system access request for execution without regard to an associated time deadline based solely upon close proximity between an information storage system address of said at least one additional storage system access request and an information storage system address of said selected one or more of said plurality of information storage system access requests comprises means for selecting at least one additional information storage system access request for execution without regard to an associated time deadline based solely upon said at least one additional information storage system access request having a storage system address within one thousand cylinders of a storage system address of said selected one or more of said plurality of information storage system access request.