The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 02, 2003
Filed:
Jan. 19, 2000
Nimrod Megiddo, Palo Alto, CA (US);
Spencer Ng, San Jose, CA (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
Upon receiving a read command, a disk drive moves a read head to target data and reads the data into a read buffer. In an action called “prefetching”, the drive continues to read nearby data into the read buffer which doubles as a data cache. When another I/O command is present and must be serviced, prefetching is preempted thereby reducing the data read into the cache. Moving the head from the current I/O command to the next I/O command creates a delay comprising two components: seek time and rational latency. Based on the relative values of these components, a time period, less than the entire delay period, is calculated in which prefetching will continue. By continuing prefetching instead of preempting it, the likelihood of cache hits is increased because more data is available in the read buffer. Furthermore, by performing prefetching during part of the otherwise unused delay period, no performance penalty is introduced.