Browse Prior Art Database

Parallel Command Processing for Small Computer System Interface Mirror Drive

IP.com Disclosure Number: IPCOM000114940D
Original Publication Date: 1995-Feb-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Iwasa, H: AUTHOR [+4]

Abstract

Disclosed is the parallel command processing for Small Computer System Interface (SCSI) mirror drive. The mirror drive controls 2 Hard Disk Drive (HDD). This is one of the RAID systems called RAID level 1. If multiple initiators accessed this mirror drive, then the first accessed host system is assigned to only one HDD and the other host system is assigned to the rest of the HDD to proceed the process concurrently.

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Parallel Command Processing for

Small Computer System Interface Mirror
Drive

      Disclosed is the parallel command processing for Small Computer
System Interface (SCSI) mirror drive.  The mirror drive controls

2
Hard Disk Drive

(HDD).  This is one of the RAID systems called RAID
level 1.  If multiple initiators accessed this mirror drive, then the
first accessed host system is assigned to only one HDD and the other
host system is assigned to the rest of the HDD to proceed the process
concurrently.

The Figure shows an example of the parallel command processing of
this disclosure.
  1.  HOST-A starts Selection of the SCSI phase and issues the 1st
READ
       command to this mirror drive.  This mirror drive receives that
       command and disconnects the SCSI bus.
  2.  Mirror drive controller passes the command only to HDD-A for
       HOST-A under multiple initiator condition.  (If it is not
under
       the multiple initiators condition, then the command must be
       passed to HDD-B as the mirror drive controller.) Then HDD-A
       starts the process of the 1st READ command.
  3.  HOST-B starts Selection of the SCSI phase and issues the 2nd
READ
       command to this mirror drive.  This mirror drive receives that
       command and disconnects the SCSI bus.
  4.  Mirror drive controller passes the command only to HDD-B for
       HOST-B under the multiple initiator condition.  Then HDD-B
starts
...