Browse Prior Art Database

Write-Back Cache for Single Ring Buffer

IP.com Disclosure Number: IPCOM000118388D
Original Publication Date: 1997-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Kanamaru, A: AUTHOR [+3]

Abstract

Write Transfer Complete: If there is a cache control block(*1) whose valid length(*2) equal to 0 Modify cache control block for keeping write back data endif Assert IREQ Next Read Command if next command hits to write back cache transfer all valid data even if media write is on going endif Note *1: Cache control block is a group of registers which controls the relations between sector buffer and media data. *2: Valid length indicates the number of LBAs which are kept in the each read buffer. Fig. 1 Algorithm

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Write-Back Cache for Single Ring Buffer

      Write Transfer Complete:
      If there is a cache control block(*1) whose valid
       length(*2) equal to 0
        Modify cache control block for keeping write back data
      endif
      Assert IREQ
    Next Read Command
      if next command hits to write back cache
        transfer all valid data even if media write is on going
      endif
  Note *1: Cache control block is a group of registers which
            controls the relations between sector buffer and
            media data.
       *2: Valid length indicates the number of LBAs which are
            kept in the each read buffer.
                     Fig. 1  Algorithm

      Disclosed is a Write-Back Cache algorithm for a Hard Disk Drive
(HDD) which has a Single Ring Sector Buffer.  Write-Back Cache means:
when a read command is issued to the same location of the previous
write command, HDD transfers the buffered data without reading media
data.  This algorithm and buffer method realizes the best performance
of a Write-Back Cache.

Fig. 1 shows the flow chart of this cache algorithm.  The major
advantages of this algorithm are:
  1.  Command overhead time does not increase because these
       microcodes are executed on head-seeking or writing to media.
  2.  If all cache control blocks have buffering data, write-back
       is not pe...