Browse Prior Art Database

ROTATIONAL POSITIONING OPTIMIZATION WITH LOOK A HEAD ALGORITHM

IP.com Disclosure Number: IPCOM000013183D
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2003-Jun-17
Document File: 1 page(s) / 27K

Publishing Venue

IBM

Abstract

Disclosed is a method to improve performance for Tagged Queue Command Reordering using a combination RPO (Rotational Positioning Optimization) and LookAhead cache.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 70% of the total text.

Page 1 of 1

ROTATIONAL POSITIONING OPTIMIZATION WITH LOOK A HEAD ALGORITHM

    Disclosed is a method to improve performance for Tagged Queue Command Reordering using a
combination RPO (Rotational Positioning Optimization)
and LookAhead cache.

When only RPO is implemented to the hard disk drive it must care Seek time, Overhead time, Rotational latency ti
preparation for Seek and Tagged Queue Command Reordering) If the host orders to process several read commands, a
two commands are continuous sectors, the drive with RPO never choose the second command as a shortest access tim
However to choose the second command makes the drive with LookAhead cache performed better throughput because th
must be hit on LookAhead cache data by the first command. The following figure explains about how to find the ne
all queued command by RPO and LookAhead cache.

FIGURE:( used pseudo code )

/* Find next queue (Next_Queue) from current queue (Current_Queue) both in Queue table (Q_TABLE) */

- Current_Queue: Pointer of current processing queue
- End_Queue : Pointer of last queue to be scanned
- Next_Queue : Next processing queue after Current_Queue
- OverHead : The time of preparation for Seek and Reordering
- Q_TABLE : Queued Commands table ( elements are bellow )

StartLBA: Start LBA to be accessed
EndLBA : End LBA to be accessed
Command : Command

:

+--------+--------+-------+-----+

Current_Queue ->|StartLBA|EndLBA |Command|.....|

+--------+--------+-------+-----+

|StartLBA|EndLBA |Command|.....|
+--------+--------...