Browse Prior Art Database

Cache Overlap Prevention Method

IP.com Disclosure Number: IPCOM000112668D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Saitoh, H: AUTHOR

Abstract

Disclosed is a procedure to prevent cache overlap during Look Ahead Buffer (LAB) operation for Hard Disk Drive (HDD) which supports multiple segmented buffers. Cache overlap means that the same data is stored in more than 2 segmented buffers. A distinctive feature of this procedure is to start another LAB his procedure is to start another LAB operation and fill another segmented buffer with other data when there is a cache overlap situation at the completion of the current LAB operation. This procedure substantially increases a valid data length in segmented buffers; hence, it increases disk performance.

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Cache Overlap Prevention Method

      Disclosed is a procedure to prevent cache overlap during Look
Ahead Buffer (LAB) operation for Hard Disk Drive (HDD) which supports
multiple segmented buffers.  Cache overlap means that the same data
is stored in more than 2 segmented buffers.  A distinctive feature of
this procedure is to start another LAB his procedure is to start
another LAB operation and fill another segmented buffer with other
data when there is a cache overlap situation at the completion of the
current LAB operation.  This procedure substantially increases a
valid data length in segmented buffers; hence, it increases disk
performance.

The technique for cache overlap prevention is described below.

1.  HDD is under LAB operation
    HDC ( hard disk controller ) is reading data from disk to a
    segmented buffer.

2.  Completion of LAB operation
    HDC completes the LAB operation and informs on the completion of
    the LAB operation to the HDD control program.

3.  Check cache overlap
    HDD control program checks cache overlap situation.  When the
    last Logical Block Address (LAB) block data which is read by the
    LAB operation is also in another segment (cache overlapped
    segment), it is considered as a CACHE OVERLAP condition.

4.  Start another LAB operation
    When the CACHE OVERLAP condition exists, the HDD control program
    starts another LAB operation from the last LBA + 1, using the
    cache overlappe...