At 03:13 PM 09/03/2000 -0400, you wrote:
>On Sun, 03 Sep 2000, Ahbaid Gaffoor wrote:
> > Hi all,
> >
> > I'm almost doen building my linux - oracle database server...
> >
> > Just one question for the SCSI experts.
> >
> > The board is a supermicro P6DBS with an onboard adaptec SCSI controller.
> >
> > I have four seagate ST12550N 50 pin SCSI drives, and the board has a 50
> > pin interface. I also have a 50 pin SCSI cd-rom and a 50 pin cable that
> > can handle seven devices.
> >
> > Here's the plan:
> >
> > Let's say the cable is numbered from the motherboard connector to the
> > last device on it as 0 through 7.
> >
> > I plan to put the cd-rom on 1, the four drives on 2 through 5, leaving 6
> > and 7 unattached.
> >
> > Do I need to get a SCSI terminator? If so, do I put it on 6? Or, if the
> > drive on 5 can be made to terminate, is that what I should do?
> >
>Put the last device on position 7 and use the on-board
>termination, if available. Otherwise, put it on 6 and use a
>terminator.
There are 3 things to keep in mind: position, SCSI ID and termination.
First, position doesn't matter. (we are dealing with signals near the
speed of light here)
SCSI ID is important. Each device must have a unique ID, in your case 0 -
7. It is settable through either jumpers or some other mechanism on the
device itself. The controller usually is ID #7 and its best to just let
this be. Beyond that, it doesn't matter what ID you give other devices.
Termination is very important. You may be dealing with older scsi devices
in which case they may or may not have built in termination. If they do
have the built in termination, it may or may not be good enough (isn't this
wonderful!!!). You are going to have to check the pinouts and figure it
out for each drive and device. The ones at the physical ENDS of the scsi
chain MUST, MUST, MUST be terminated. If the controller is the end of the
chain (you are just using the internal or external cable connection) then
the controller must be terminated. If you are using both the internal and
external connections, then the controller must be un-terminated and the
device at the end of the chain must be terminated. Again, you are going to
have to hit the docs of the controller to see what is what for the built in
termination.
HTH,
Mark
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| Mark Neidorff |Never assume a conspiracy exists |
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