ds20 servers connect to hsz80

[Bob Blunt]

Dang QLogic SCSI adapters...  I've got a stack of them...but they're 175 miles away.  You'll note that all of your bus based SCSI interfaces are listed as QLogic ISP10x0?  I'm pretty sure that there are two variants of these.  One is called the KZPBA-CA and the other is KZPBA-CB.  One is Ultra Wide Single Ended and the other is Ultra Wide Differential.  The latter is required for connection to the HSZ...REQUIRED.  The controllers are differential, not single-ended.  Unfortunately I can't eyeball the two types but on initial visual they look almost identical.  They BOTH have external HD68 connectors.  Both have an internal 68 pin and internal 50 pin connector too.  The differential KZPBA-CB can have terminators on the internal component side of the module.  I can't remember if the single-ended KZPBA-CA has plugs for terminators or not.  The stamped metal bulkhead panels MAY have a marking indicating type, some do and some don't.  Look on the metal plate attached to the adapter on the side with the external HD68 pin connector for (sorry for the primitive "art"):

                       //\            //\\                                  /\

                            --  or          --                                    --

                       \\/            \\//                                  \/

The emblems on the left are for a differential adapter and on the right for single-ended.  Those aren't an EXACT representation of the emblem stamped into the metal, the gap between the top and bottom is almost non-existant and the differences are subtle.  You might also get some clarity from these web copies of the user's manuals:

http://manx.classiccmp.org/collections/antonio/dec/MDS-2000-01/cd3/Storage/KZPBCUGB.PDF  -- differential

http://manx.classiccmp.org/collections/mds-199909/cd3/storage/kzpbaugb.pdf -- single ended

There's artwork on page 3-3 of the KZPBA-CB manual that shows where the terminator resistor SIP packs go but if they're removed it might be difficult to tell the differential from the SCSI.  Page 3-3 of the KZPBA-CA manual is similar but it doesn't look like the single-ended card has the terminators.  The KZPBA-CB manual also has a nice chapter about cables and cabling configuration that the KZPBA-CA manual doesn't have.

This is a pointer to the HSZ70 Service Manual:

ftp://ftp.hp.com/pub/openstorage/v70_hsz70_service_manual_a01.pdf

It has some moderately useful artwork showing different cabling configurations with a list of cable part numbers on pages starting at page 1-31.  Because the controllers have only one SCSI bus each the configuration should be relatively simple.  I would configure and cable for "dual redundant" mode rather than "multiple bus failover" but that is mainly personal preference.  I'd make sure that I was absolutely sure I had two differential SCSI adapters on one shared bus.  Connect those adapters with a HD68 pin Y cable (if available) on each and put a terminator on the last unconnected HD68 pin connector on the last Y cable on the bus.  MAKE SURE that there are NO terminator resistor SIP packs on either of the host SCSI differential adapters at all.  You'll need a HD68 pin to VHDCI converter or converter cable and connect that to one side of the HSZ70 controller trilink.  Use a VHDCI jumper cable between the trilinks on each controller and come off the last open trilink to either a terminator or a relatively short cable with a terminator:

Term     ____   __________   ___   Term

           \ /         \/                         \/       \/

            Y           Y                       TRI     TRI

             |            |                           |          |

            K           K                          H        H

            Z           Z                          S         S

            P           P                          Z         Z

            B           B                          7         7

            A           A                          0         0

             |            |

            C           C

            B           B

This example is from working with and trying to maintain SCSI clusters for a long time running OpenVMS.  In that environment it would be easier if the devices presented from the controllers to the operating system all had the same names.  It isn't mandatory that you follow this suggestion to the letter but I've found it the easiest to maintain when service needs arise (OK, in a rackmount configuration the length of cable between the two hosts should be long enough to pull either node out for service without causing the cables to disconnect at the wrong time.  The Y cables and trilink connectors serve a similar purpose...in this configuration you could disconnect one Y from it's host and the SCSI bus is intact and the other node could keep running and accessing storage.  Same for a controller issue, disconnect the whole trilink and leave the cables and you could replace a controller without taking down both controllers.  The KEY here is to make 100% Sure that you've got a differential SCSI adapter (preferably PKC0 on each host but NOT fully mandatory) in each host with NO termination on the SCSI adapter.

[allant-au]

Thank you for going to the trouble of providing such a detailed explanation. I have forwarded this to our hardware suppliers. It may take me some time to digest all the details before I try any reconfiguration.

Regards,

Allan Thorne