Browse Prior Art Database

Hard Disk Drive Read Cache Method Utilizing Fat Table

IP.com Disclosure Number: IPCOM000114333D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Asano, H: AUTHOR

Abstract

This article describes the read cache prediction method of Hard Disk Drive (HDD) read operation by referring the File Access Table (FAT) which controls HDD file store sequence for the host access.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 79% of the total text.

Hard Disk Drive Read Cache Method Utilizing Fat Table

      This article describes the read cache prediction method of Hard
Disk Drive (HDD) read operation by referring the File Access Table
(FAT) which controls HDD file store sequence for the host access.

      The host reads the file allocation table from HDD after
Power-On which includes the BOOT parameter, the BIOS parameter, and
FAT.  Then booting the host will start.  This article describes DOS
FAT case but the method is the same in OS/2* HPFS.  Initial data
accessed by the host are shown in Fig. 1.

      HDD read data flow is shown in Fig. 2.  After the read
operation, HDD continues to read data for the continuous sectors in
the same cylinder to prepare the next read operation which improves
the read performance if the next read command is to read data from
the look ahead area.

      This sequence follows MPU in HDD reads FAT table after POR,
stores it in the local RAM area, and builds the address chain table
by searching the address chain per each file name in the FAT table.
When the host sends the read command, then HDD reads data from the
disk and checks the file name in the address chain table to predict
the potential next address to be accessed.  After the read command
completes, HDD starts to read the data of the predicted address and
stores in the sector buffer.  When the next read command sent from
the host, the HDD checks whether the read address meets the predicted
one or not.  If...