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Predicted Seek in HDD

IP.com Disclosure Number: IPCOM000013639D
Original Publication Date: 2000-Feb-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Abstract

Predicted Seek in HDD This method is to shorten the seek time relatively by predicting the next logical block address (LBA) accessed by the commands issued from the system to the Hard Disk Drive (HDD). If HDD can predict the flow of Data stream between PC system and HDD, then HDD will seek to the next accessing location before the next command comes. If this hit ratio is high, it improves the seek time virtually. This method is to start the virtual seek operation after the look ahead operation for the read command or before the write cache operation for write command. Therefore even the target location is different from the predicted one, additional seek is minimum or none. This prediction is effective in the normal PC environment as there are two main areas to be accessed, File Allocation Table (FAT) and the data area. Detail explanation is for read command. This method defines the read command blocks up to m, and if LAB difference from the previous read command is within the range of n then it handles as next read command as same block read command. When the read command comes, HDD save the first LBA to the first read block table. HDD checks the first LBA of next read command whether LBA is within the range of first read command LBA n, and if it is within the range, then change the LBA stored in the first block to the new one. If the next read command is out of the first block range, then save the new LBA to the second read block table. After filling up to the m blocks, next saving location is to the table least updated.

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Predicted Seek in HDD

Predicted Seek in HDD

This method is to shorten the seek time relatively
by predicting the next logical block address (LBA)
accessed by the commands issued from the system to
the Hard Disk Drive (HDD).

If HDD can predict the flow of Data stream between
PC system and HDD, then HDD will seek to the next
accessing location before the next command comes.
If this hit ratio is high, it improves the seek
time virtually. This method is to start the virtual
seek operation after the look ahead operation for
the read command or before the write cache
operation for write command. Therefore even the
target location is different from the predicted
one, additional seek is minimum or none. This
prediction is effective in the normal PC
environment as there are two main areas to be
accessed, File Allocation Table (FAT) and the data
area.

Detail explanation is for read command.
This method defines the read command blocks up to
m, and if LAB difference from the previous read
command is within the range of n then it handles as
next read command as same block read command. When
the read command comes, HDD save the first LBA to
the first read block table. HDD checks the first
LBA of next read command whether LBA is within the
range of first read command LBA +/- n, and if it is
within the range, then change the LBA stored in the
first block to the new one. If the next read
command is out of the first block range, then save
the new LBA to the second read block table. After
filling up to the m b...