Browse Prior Art Database

Seek Minimization

IP.com Disclosure Number: IPCOM000075410D
Original Publication Date: 1971-Sep-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Anderson, WH: AUTHOR [+3]

Abstract

Minimization of seek time on moveable head direct-access storage devices may be achieved in the following manner:

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Seek Minimization

Minimization of seek time on moveable head direct-access storage devices may be achieved in the following manner:

Requests for file records are placed in a seek queue 1 and ordered in ascending sequence in accordance with the cylinder number of the location of the record. Each request is forward and back chained in the queue. In the illustration, four requests R1-R4 are in the queue and the respective records are located on cylinders 35,22,42 and 29. The requests are chained in the order of ascending cylinder numbers.

Any new requests such as R5, are added to the queue at the appropriate point in the chain.

Requests are dequeued from seek queue 1 by either a selection processor 2 or sequential seek routine 4. When a request has been dequeued, it is set up as a seek item 3 and the information which chained the request within the seek queue is retained in the seek item. When a new seek is to be made, selection processor 2 looks to this chaining information associated with the last seek item, and looks in both forward and rearward directions to determine which request is for a cylinder number that is closest to the cylinder number associated with the current position of the direct access heads. This closest cylinder number would then be selected for the next seek. In the illustration, the last seek was on cylinder 25. Request R2 for cylinder 22 is the closest and will be the next request for which a seek is done.

To prevent a possible lockout situa...