Very Computer

by **Jeffrey Ros** » Fri, 17 Jan 2003 12:04:03

We have 3 of these machines, none of which has a SCSI terminator.
The bus drives the internal CD only. I sometimes hot-plug an external tape
drive into the bus for backup.
One of the 590s lost its SCSI adaptor recently. Could be the fuse has
gone - currently working on it.
According to the manual I shouldn't be hot-plugging and must have a
terminator.
Is this really true? It doesn't seem to have been a problem over the past 5
years...
Any advice?
Jeffrey.

by **Iai** » Fri, 17 Jan 2003 21:21:55

> The bus drives the internal CD only. I sometimes hot-plug an external tape
> drive into the bus for backup.

99% of the time hot-plugging is only a problem in that it interrupts
other devices on the same bus. In your case, you have a CD on the bus
and you hot plug (or unplug) a tape drive. This is very unlikely to
cause a problem unless the CD is in use (reading) at the moment you
make a change. If it was another tape device or a disk drive instead
of the CD you would see a lot more problems.

No idea about the terminator though.

Iain.

by **Benjamin Gawer** » Sat, 18 Jan 2003 05:42:10

> We have 3 of these machines, none of which has a SCSI terminator.
> The bus drives the internal CD only. I sometimes hot-plug an
> external tape drive into the bus for backup.
> One of the 590s lost its SCSI adaptor recently. Could be the fuse has
> gone - currently working on it.
> According to the manual I shouldn't be hot-plugging and must have a
> terminator.
> Is this really true? It doesn't seem to have been a problem over the
> past 5 years...
> Any advice?

Hot-Plugging on not hot-plug-ready equipment is always a very high risk. In
most cases it works but doing a hot-plug with connectors that arent made
for hot-plugging (means: closing ground connection before closing signal
connections) always includes the risk of frying Your equipment due to
differences in the equipments electrical ground potential...

As to the terminator: You should have one. Sure, mostly it works, but You
risk data corruption due to signal reflections on the not-terminated side of
the bus and may cause other strange errors....

Benjamin

by **Jose Pina Coelh** » Sat, 18 Jan 2003 12:10:26

> I sometimes hot-plug an external tape drive into the bus for backup.

SCSI is not hot-pluggable per se. Some active backplanes on machines
like the F50, allow you to hot-plug a disk into the bus. Anything else
is risking data corruption.

> According to the manual I shouldn't be hot-plugging and must have a
> terminator.
> Is this really true?
As to external SCSI buses: they are not hot pluggable and the common
result is a blown card/fuse. They all require termination, unless the
last device is auto-terminated.

> It doesn't seem to have been a problem over the past 5 years...
If the external SCSI is very short, it can run quite a long time without
visible errors (they can be there, nontheless), the result being mashed
backups and a false sense of security.

--
Doing AIX support was the most monty-pythonesque
activity available at the time.
Eagerly awaiting my thin chocolat mint.

Very Computer

Does a 590's inbuilt SCSI bus really need a terminator?

Does a 590's inbuilt SCSI bus really need a terminator?

Does a 590's inbuilt SCSI bus really need a terminator?

Does a 590's inbuilt SCSI bus really need a terminator?

Does a 590's inbuilt SCSI bus really need a terminator?