Method and apparatus for sorting disk access commands in a rotat

Details Method and apparatus for sorting disk access commands in a rotat Method and apparatus for sorting disk access commands in a rotat

1994-11-23

1997-09-02

Harvey, Jack B.

Electrical computers and digital processing systems: memory

Storage accessing and control

Specific memory composition

G06F 1200

Patent

active

056641435

ABSTRACT:
A method and apparatus for sorting a rotational position queue without sensing the rotational position of a recording media in a disk drive. Commands are accepted into a rotational position queue. A first command is selected and assigned the physical address of the last requested block of the first command. Each of the remaining commands are assigned the physical addresses of their first requested block. The difference between the physical address associated with the first command and each of the other commands is computed. The address differences are converted into a corresponding time difference. A seek time is subtracted from each time difference and, for the unselected commands having a time difference less than zero, a modified time difference is calculated by adding a full revolution latency time. The time differences are sorted according to their magnitude to identify the command associated with the smallest time difference. This command is labeled as the next command which is then assigned as the first command after the first command is dequeued. After each first command is dequeued, the process is repeated to ascertain a new next command.

REFERENCES:
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patent: 5345561 (1994-09-01), Kato
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patent: 5463758 (1995-10-01), Ottesen
IBM, "Enhanced Disk Task Scheduling", IBM Technical Disclosure Bulletin, vol. 29, Nr. 5, pp. 1946-1948 Oct. 1, 1986.
Hwang et al., "New Disk Scheduling Algorithms for Reduced Rotational Latency", Proceedings of the Third International Symposium on Database Systems for Advanced Applications, pp. 395-402 1993.

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