21 Jun
2002
21 Jun
'02
2:48 a.m.
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(a)classiccmp.org [mailto:cctalk-admin@classiccmp.org]
On Behalf Of Huw Davies
Sent: Friday, June 21, 2002 10:12 AM
To: cctalk(a)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(a)kerberos.davies.net.au
| "If God had wanted soccer played in the
| air, the sky would be painted green"