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Input/Output Bus Controller for Hard Disk System Utilizing the Hard Disk Drive's Cache

IP.com Disclosure Number: IPCOM000114580D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Munetoh, S: AUTHOR [+4]

Abstract

Disclosed is an Input/Output (I/O) bus controller for a hard disk system. The controller improves the I/O bus utilization by releasing the I/O bus, when it predicts the long access time of Hard Disk Drives (HDD) included in the hard disk system. The controller predicts the access time by recording the access to each HDD and predicting the cache contents of that.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 58% of the total text.

Input/Output Bus Controller for Hard Disk System Utilizing the Hard
Disk Drive's Cache

      Disclosed is an Input/Output (I/O) bus controller for a hard
disk system.  The controller improves the I/O bus utilization  by
releasing the I/O bus, when it predicts the long access time of Hard
Disk Drives (HDD) included in the hard disk system.  The controller
predicts the access time by recording the access to each HDD and
predicting the cache contents of that.

      Fig. 1 shows the example of the HDD system using this
invention.  This HDD system consists of Bus IF with host system's I/O
bus, MCU, ROM, RAM, DMAC, Tag, and HDDs.  Tag is the main device to
construct the I/O bus controller using this invention.  Fig. 2 shows
Tag's structure.  Tag consists of valid flag, LBA, Len, and AccessNo.
Valid flag shows whether the contents of Tag is valid or not.  LBA
shows the top logical block address (or cylinder head sector) of the
access.  Len shows the length of the access.  AccessNo shows the
sequence number of the access recorded in the Tag.  In the following,
the method to initialize Tag, and to control Tag, HDD, I/O bus in
read/write are described.

Tags are initialized by filling the value "invalid" in valid flag.

      In read, the lba and len of the access are compared with LBA
and Len of Tag whose valid flag's value is "valid".  When the access
area matches the contents of a Tag, namely, the data is predicted to
be cached, the corresponding Tag's Acce...