SUMMARY -- Too many disks on an SS2

From: Charlie Dennett (
Date: Thu Sep 12 1991 - 17:11:52 CDT

Here is my original posting:

----- Begin Included Message -----

Subject: Too many disks on a SS2?
Status: R

I have (or should I say had) a Sparcstation 1 that was running 4.0.3c.
It had two internal Quantum 105 disks (sd0 - scsi id3, and sd1 - scsi
id0). It also had 4 external Hitachi 312C-25 disks (sd2-sd5). This
Sparcstation 1 was upgraded to a Sparcstation 2. This involved moving
the internal disks to the new pizza box. I put the external disks on
the Sparcstaion 2's scsi bus. I had all sorts of trouble getting the
new 4.1.1 OS loaded from cdrom when the external disks were attached so
I installed the OS without the external disks.

After I got 4.1.1 up I built a new kernel to support all the disks.
The kernel loads and proceeds with the bus probe. It sees the first
internal disk but then hangs on the second internal disk. I discovered
that if I disconnect any one of the four external drives it boots with
no problem. It can handle 5 disks but will not handle 6. It makes no
difference which external disk I unplug. By the way, all four of the
external disks are in one cabinet. When I said I disconnected one of
them what I really did was disconnect the power to one of the disks.
The scsi connections remained.

Does anybody have any suggestions? I did not try disconnecting just
one of the internal disks.

Thanks for any help.

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First of all, thanks to everyone who took the time to offer
suggestions. Several people said that perhaps there was a duplicate
scsi id on the bus. This was not the case. Remember that all these
disks were on a SS1 before the upgrade and were simply moved to the
SS2. The kernal was remade to support these disks just like it was on
the SS1. Also, it did not make a difference which disk I disconnected
as long as I disconnected one. When I did that each of the remaining
disks were seen correctly by the kernel.

Several people also suggested that the total scsi cable length was too
long. The spec says (I believe) 6 meters (18 feet). This includes all
wiring inside the cabinets. Well, I had a 6 foot cable connecting the
SS2 to the external disk cabinet. There is only about 2 or 3 feet of
cable connecting the external disks together. I don't know what the
"length" is inside the SS2. Does anyone know? Also, does anyone know
if the various connectors add a significant length to the cable?

Anyway, I swapped the 6 foot cable for a 3 foot cable and the system
booted successfully with all six disks. (I borrowed the cable and had
to reinstall the 6 footer so I'm back to 5 disks until I can get a new
cable of my own.) So, it appears to be a problem with the length of
the scsi cable. I didn't think I was even close to the limit but maybe
with all those disks, the limit is a lot less. Either that or perhaps
there is a significant amount of cable length internal to the SS2 or
perhaps the connectors add a significant amount of length.

(I also owe you people a summary on scsi addressing as it applies to
VME based kernels. The kernel config files specify the
scsi addressing a little differently from the s-bus based kernels.
That will be forth coming in a day or two.)

Charlie Dennett | Rochester Distributed Computer Services
Mail Stop 01816 | Customer Technical Site Services
Eastman Kodak Company |
Rochester, NY 14650-1816 | Internet: dennett@Kodak.COM

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