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From: awpsys@ultb.UUCP (Andrew W. Potter)
Newsgroups: comp.sys.dec
Subject: Re: Tape Drive tricks on VMS & Ultrix
Message-ID: <1514@ultb.UUCP>
Date: 30 Oct 89 23:58:24 GMT
References: <12329.25472184@vaxb.acs.unt.edu>
Reply-To: awpsys@ultb.UUCP (Andrew W. Potter)
Organization: Rochester Institute of Technology, Information Systems
Lines: 67

In article <12329.25472184@vaxb.acs.unt.edu> billy@vaxb.acs.unt.edu writes:
>
>I am planning some upgrades and wonder if the following will work:
>
>    VAX 6310  DECsystem 5810
>       |        /             
>    HSC 50     /
>       \      /
>        \    /
>         \  /
>         TA78 tape drive
>

Your diagram is not entirely accurate.  Note that TA tape drives can ONLY
be connected to an HSC controller. So what you can do is:


	a) Put a CI in your 5810 and connect it to the same CI that your
           VAX 6310 is connected to.  Note that if you are running VMS
           on the 6310, the configuration will be unsupported, but WILL
           work if you are carefull about keeping ultrix and VMS away from
           each others disks.  They can even share the same HSC and HSC disk
           and tape channel cards.   The only thing they cannot access at the
           same time is the actual devices (A disaster if this occurs on
           your disks).  I posted a lengthy note a while ago about mixing
           A VMS CLuster with Ultrix over the same CI.

	b) Get a second HSC, and put a CI in your 5810 and Dual port the
           TA78 between the two HSCs.  You then have manual switching whish
           is safer and you keep your disks separate.  You would have the CI
           attached to the 5810 and the second HSC creating a completely
           separate CLuster Interconnect from the one on your 6310

Pictorially the options would look like:


a)     6310           5810
        \_____CI______/
                 \
                  HSC
                 /   \
            Disks     Tape (TA78)




B)    6310                     5810
        \___CI__o      o__CI___/
              \          /
             HSC        HSC
            /   \      /   \
       Disks     \    /     Disks
                  TA78

Option B is obviously a lot more expensive.  Also, If you already have
multiple HSCs on your VMS cluster and are dual porting the TA78 between
tape requestors on two HSCs for reliability, you would not be able to
use option b.


- Andy

-- 
Andrew W. Potter                 Bitnet:   awpsys@ritvax.BITNET
Systems Programmer               Internet: awpsys%ritvax.bitnet@cunyvm.cuny.edu
Information Systems and Computing
Rochester Institute of Technology, Rochester NY, 14623 (716) 475-6994