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Re: tail of two scsis



From: "Jose Luis Ricardo Chavez" <ricardo irsamc ups-tlse fr>
> Richard Emberson wrote:
> 
> > Jose Luis Ricardo Chavez wrote:
> >
> >> Richard Emberson wrote:
> >>
> >>> Jose Luis Ricardo Chavez wrote:
> >>>
> >>>> Richard Emberson wrote:
> >>>>
> >>>>> I've got a FC2 system and a scsi disk with /boot and /.
> >>>>> In addition, I have two other scsi disks with /home and /usr/local
> >>>>> on them (call the disks A and B). Both of these disks
> >>>>> have their IDs set to 6.
> >>>>> When I boot the system with disk A, disk A can be found and
> >>>>> the boot succeeds. When I replace disk A with disk B, disk B
> >>>>> can not be found and the boot fails.
> >>>>> Other than the possibility that disk B is bad, what else
> >>>>> could be the cause?
> >>>>>
> >>>>> The boot disk is a 7500rpm Quantum.
> >>>>> Disk A is a 10000rpm Maxtor.
> >>>>> Disk B is a 7500rpm Quantum.
> >>>>> Back in my RedHat 9 days, the system used both Quantum disks.
> >>>>>
> >>>>> Thanks
> >>>>>
> >>>>> Richard
> >>>>>
> >>>>>
> >>>> Are both disks using the same SCSI id while connected to the same 
> >>>> cable
> >>>> (SCSI channel)? As far as I remember there is not a "cable select" 
> >>>> option
> >>>> when using SCSI disks, both disks should use different id's. Put 
> >>>> the lowest
> >>>> id on the boot disk (A). If the disks are connected to different 
> >>>> SCSI channels
> >>>> then maybe there is a problem with one of them.
> >>>> - Jose Luis
> >>>>
> >>>>
> >>> The boot disk is always on the cable. Only one of the disks A and B
> >>> are on the cable at one time.
> >>>
> >>>
> >> Ok, you have three disks, the boot disk is permanently connected and 
> >> you connect
> >> disk A or B when needed. Is the SCSI BIOS detecting disk B?
> >
> >
> > No.
> > It detects disk A (disk B not connected) but not disk B (disk A not 
> > connected).
> > The boot disk in both cases is detected.
> >
> >>
> >> - Jose Luis
> >>
> >>
> >
> >
> Well, it seems disk B is damaged.

Or as someone else commented here he is installing the B drive at the end
of the cable and it is not terminated.

SCSI terminations are critical. You need ONE termination at EACH END of
the SCSI chain. If the chain extends both inside the machine and outside
the machine you still need terminations at the two ends of the chain and
the controller needs to be unterminated. You also MUST install drives or
terminations on the last connectors on the SCSI chain, not somewhere in
the middle.

{^_^}



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