topic Re: SCSI Terminator and bus problem in Disk

SCSI Terminator and bus problem

Sebastien Masson — Wed, 21 Nov 2001 11:43:59 GMT

I all,

I have some K-Class with some Jamaica that I want to connect together to build a MC ServiceGuard cluster and I run into trouble with shared SCSI bus.

Do I need the terminator on SCSI card at both end ? Do I use the inline terminator cable (small black cable) instead ?

Because when I connected everything together, The both system wont boot. I check to be sure my SCSI ID are uniq on the bus, but now I think is't a terminator problem.

Any help wanted.... :-)

Re: SCSI Terminator and bus problem

Alexander M. Ermes — Wed, 21 Nov 2001 12:41:22 GMT

Hi there.
Usually you have terminators on the interface.
For the Jamaica you need an active terminator for each channel, if you connected machine A to channel 1 and machine B to channel 2.
Rgds
Alexander M. Ermes

Re: SCSI Terminator and bus problem

Patrick Wessel — Thu, 22 Nov 2001 20:07:32 GMT

Sebastien,
One of the basic rules of SCSI is: you need exactly two terminators in a SCSI bus, one on each end.
If you use inline terminator cable, you need two (one for each end). Or keep the terminators on the host bus adapter. It's your own choise, as long as you have both ends terminated

Re: SCSI Terminator and bus problem

Sebastien Masson — Fri, 23 Nov 2001 13:09:16 GMT

So, the only time you need to remove terminator on SCSI controler is when you use the inline term scsi cable (little black cable) ?! And if I use this cable, I need to remove terminator on both controler and use it at both end ?! The think is I don't understand the position of SCSI terminator on the BUS.

You said at both end, but the inline cable is between the controler and the bus...

Re: SCSI Terminator and bus problem

Patrick Wessel — Sun, 25 Nov 2001 21:22:21 GMT

Sebastian,
You are right; in fact, the controller is the last device on the bus, not the terminating cable. But that is just 1 or 2 inches and not such a big deal.
When you use 3 or more SCSI host bus adapter (as an example: in a 3 node cluster), you should also remove the terminators from the HBA to have not more than 2 terminators in the bus