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Conference ssag::ask_ssag

Title:Ask the Storage Architecture Group
Notice:Check out our web page at http://www-starch.shr.dec.com
Moderator:SSAG::TERZAN
Created:Wed Oct 15 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:6756
Total number of notes:25276

6700.0. "dual-rail SCSI with OVMS 7.1" by TROOA::MSCHNEIDER ([email protected]) Mon May 19 1997 09:58

    It is my understanding the OVMS 7.1 provides support for dual-rail
    SCSI to avoid single points of failure.  I'm trying to understand how
    this is physically implemented.  Am I correct in the following
    implementation assumptions:
    
    				     BA350 ctlr shelf
    				+-------------------+
    				|		    |
    KZPSA ----------------------+ HSZ50		    |
                                |		    |
    KZPSA ----------------------+ HSZ50		    |
    				|	            |
    				+-------------------+
    				   |  |  |  |  |  |
    				   |  |  |  |  |  |
    
    				    SW disk shelves
    
    
    Is there still a cable linking the 2 HSZ50 controllers as there would
    be if they were connected to a single KZPSA?
    
    Have I effectively doubled my bandwidth to the host with 2 FWD SCSI
    paths to the host or is it a redundant alternative path that is not
    used except in event of failure?
    
    
    Thanks,
    
    Martin
    DTN 626-3180
T.RTitleUserPersonal
Name
DateLines
6700.1No dual-rail failover in V7.1SSDEVO::MARTENSBert Martens, CXO Storage SolutionsMon May 19 1997 10:088
    Martin,
    
    Currently there is no support for multi-bus failover in OpenVMS. Future
    functionality should be directed toward Product Managers.
    
    
    Bert
    
6700.2wishful thinking perhaps.....TROOA::MSCHNEIDER[email protected]Mon May 19 1997 10:4910
    Thanks Bert for the quick correction.  I just reread the New Features
    guide to OVMS 7.1 where I thought I had seen this and the only change
    for 7.1 is the support of high SCSI IDs.  Don't know how I thought
    dual-rail was supported ....
    
    ;^)
    
    
    
    
6700.3Multi-Rail SCSI Failover: Possible Future SupportXDELTA::HOFFMANSteve, OpenVMS EngineeringMon May 19 1997 13:087
   There was another discussion on this recently -- see VAXAXP::VMSNOTES
   562.* -- as OpenVMS engineering is presently evaluating the design and
   the addition of the code changes necessary for support for a pair of
   HSZnn controllers "back-to-back" off a pair of SCSI busses.  (Don't
   try this stunt at home yet, though...)

6700.4thanks for the pointer....TROOA::MSCHNEIDER[email protected]Mon May 19 1997 13:266
    This would be very useful to eliminate the two single points of failure
    that exist even with paired HSZxx controllers, namely the KZPSA and the
    BN21K cable.  It also gives a nice bandwidth boost.
    
    The UNIX folks have promised it in the Steel release and I mistakenly
    had thought that 7.1 delivered it with VMS.