One SCSI tape connected to 2 hosts?

From: Richard Erlacher <edick_at_idcomm.com>
Date: Fri Jun 21 18:13:51 2002

I rather hate to tell you this, but, backing up Windows, depending, I guess,
on which software package in use at the time, your tape drive will occasionall
disappear anyway. I've yet to see a backup package, for Windows 9x anyway,
that doesn't lose SCSI tape drives from time to time. In fact it doesn't
manage removabel SCSI disk drives terribly well either.

In short, it's not the tape drive or the SCSI hookup, probably, but is more
than likely the stupid and short-sighted way in which the SCSI subsystem under
Windows is implemented.

What you might find works pretty well, as compromises go, is to put a
terminator at the tape drive, assign it the appropriate address, and simply
attach it to one subsystem or the other as needed.

Dick

----- Original Message -----
From: "Bob Lafleur" <bob_lafleur_at_technologist.com>
To: <cctalk_at_classiccmp.org>
Sent: Friday, June 21, 2002 8:48 AM
Subject: RE: One SCSI tape connected to 2 hosts?


> I guess I've abandoned the idea of hooking the tape drive to both
> systems. It sort of worked, but I found when I had it connected this
> way, when backing up under Windows, the drive would suddenly become
> unavailable. Sometimes it would run for an hour, and then this would
> happen. I don't know if the VMS system was sending it a reset, or what.
> I didn't use it enough under VMS to know if Windows was interfering from
> that side, but I did a few medium length tests and it seemed to be OK.
>
> I'll just throw the DDS-2 drive into the MicroVAX (I might have to use
> some sort of mickey-mouse mounting system if I can't find a mounting
> bracket for a BA42B case) and find another drive for the PC.
>
> - Bob
>
> -----Original Message-----
> From: cctalk-admin_at_classiccmp.org [mailto:cctalk-admin_at_classiccmp.org]
> On Behalf Of Huw Davies
> Sent: Friday, June 21, 2002 10:12 AM
> To: cctalk_at_classiccmp.org
> Subject: Re: One SCSI tape connected to 2 hosts?
>
>
> At 03:16 PM 16/06/2002 -0500, Doc wrote:
> >On Sun, 16 Jun 2002, Bob Lafleur wrote:
> >
> > > I've noticed that my MV3100's SCSI host ID's are set to 6 - I
> > > thought this odd, as host ID's are usually 7. Are all MV3100's set
> > > to 6, or is mine unique? Anyway, I thought since my PC's host ID is
> > > 7, I could connect my SCSI tape drive to both systems. So I ran a
> > > cable from one connector on the back to my PC, and a cable from the
> > > other connector to my MV3100. I figure it's a properly terminated
> > > chain, as each host controller is terminated (I know the PC is, I
> > > assume the MV3100 is).
> > >
> > > It *seems* to work OK. But can anyone tell me for sure if this is
> > > "legal"? I'm sure I'm looking for trouble if I try to use the same
> > > tape drive from both systems at the same time, but as long as I
> > > don't do that, is this an okay setup? It would sure beat changing
> > > cables every time I want to move the tape drive from one system to
> > > the other.
> >
> >Bob,
> > A few of the older SCSI "how-to" pages diagrammed just such a setup.
>
> >I've never seen it done in real life, but it always looked like a
> >reasonable idea to me, too.
> > I just found out, talking to my boss, that both native Solaris and
> >Veritas Volume manager support that type of configuration.
> > It's also relevant that you can run IP-over-SCSI between hosts, and
> >ISTR that the original Beowulf code provided just that for fast
> >intra-cluster communication.
>
> Of course Digital (and Compaq) supported systems with shared SCSI
> storage
> under OpenVMS alpha - not surprisingly they were known as SCSI clusters.
>
> You still needed ethernet for SCS traffic but it certainly worked.
>
> Huw Davies | e-mail: Huw.Davies_at_kerberos.davies.net.au
> | "If God had wanted soccer played in the
> | air, the sky would be painted green"
>
>
>
Received on Fri Jun 21 2002 - 18:13:51 BST