HP DAT72 and disks on same bus on a PWS

[Bengt Nilsson_2]

I have severe difficulties on a PWS433 (or a PWS500, same behaviour ) to have disks and a HP DAT72 tape device on the same SCSI bus, the disks come and go at random or no devices show up at all, including the tape.

Is this a know problem?
Any remedy except having a extra SCSI interface dedicated to the tape?

[Steven Schweda]

Shorter cables? Proper termination? Where
are all these devices? Internal? External?
With single-ended SCSI, it's difficult to
have both on one adapter without exceeding
the maximum cable length (which can be
remarkably short).

On my main XP1000, internally I have two hard
disks and a DVD-ROM drive on the on-board
SCSI, and externally, a tape (DLT), a hard
disk, and a CD-R/RW drive on a KZPBA-CX card
(which has nothing connected internally).

You may not need a SCSI card dedicated to the
tape, but you may need one (or more) cards
dedicated to external devices.

[Bengt Nilsson_2]

The problem is internal or external, short or long cables (how long is short/long? I have an internal cable about 40 cm long), with and without termination, anything you would suggest.
Right now I have it connected to an extra scsi card, and it works. The only painful thing is the PCI scsi external connector, that is useless since if I connect anything to it, the tape stops working and the connected device is never detected if I do. So I will have to tape it over with red tape.

[Bengt Nilsson_2]

I have got a hunch that the problem may be that of HVD / LVD / SE bus compatibility.

The HP DAT72 is a LVD/SE device, the specs says.

What kind of bus do we have in a PWS500? HVD or LVD?

[Steven Schweda]

> [...] (how long is short/long? [...]

40cm should be short enough. A Web search
for keywords like "scsi cable length" should
find some opinions/facts. External cables
tend to be longer than they look because of
the cable hidden inside drive enclosures.

> [...] with and without termination [...]

Where is "with"? Some devices have built-in
terminators which may need to be disabled.
You should have only one terminator at each
("terminal") end of the cable.

> What kind of bus do we have in a PWS500?
> HVD or LVD?

SE, normally. LVD devices should be able to
adapt to single-ended environment, however.
(Most of my hard disks are LVD/SE, for
example.)

[Rob Leadbeater]

Hi,

This sounds to me, almost certainly a termination issue. As Steven suggested, you may have something double terminated, especially if you're trying to use, both internal and external connectors of a SCSI card.

Cheers,

Rob

[Bengt Nilsson_2]

"Both" meant of course not double termination, just that I tried both with a terminated cable, as well as a cable with terminator. None worked.

Now, I got some success.
I saw on the HD that there was a strap "force single-ended mode". I put a strap on it and then it actually seemed to work. However it has been working now and then before, so time will tell.

Seems like mixing old and new devices may cause problems.
Again, what mode is most probably used by the QLogic and on-board controllers in a PWS500?

[Bengt Nilsson_2]

Sorry, I missed that you already answered the SE/LVD question.

[Bengt Nilsson_2]

My conclusions were too fast. "Force single sided" did not do the trick. The tape and the disks showed up properly at the >>> prompt, but once booted the tape was missing.
So the disks were operable but not the tape.
I tired both with a terminated cable and an unterminated, same result.

BTW: What does the strap "Term power" mean?

[Steven Schweda]

> BTW: What does the strap "Term power" mean?

Power for the terminator resistors (et c.,
depending on how fancy the terminator is).
Someone on the bus must supply it, but one
source is enough. (It's normally safe to
have more than one source. They're designed
to coexist with others.)