SUMMARY: Unable to add two hard disks

From: Ricardo Ruiz SSD (
Date: Thu Dec 22 1994 - 14:54:33 CST

Thank you very much to all the persons that replied to my original
message. I am still searching for an explanation to my problems but
decided to remove one of the disks and attach it to another SPARC.

Below is a list of the recommendations I received and a comment or two
of what was done about it.

- Look in the file /usr/sys/sun4m/conf/GENERIC.

I did and it contains the original information; sd0, 1, 2, and 3 on esp0.

- What does probe-scsi (at the boot monitor) tell you about your devices?
Do you have target ID conflicts?

No conflicts. probe-scsi comes back with the information I expect.

- Your SCSI - cabling seems to be too long - try to use shorter ones.

Many persons recommended using shorter cables. The cables are long: 44"
for the Centronics to SCSI-2 type (1), 37" for the SCSI-2 type (2), and
37" for the Centronics type (2). I removed the the CD-ROM and tape drives
to use two less cables but the system kept hanging when there were three
external hard disks in the chain. The total cable length was 10'.

- They are probably "internaly terminated". Did you remember to clip the
terminators out?

Another popular response. I checked with the supplier and the specs.
They are not internaly terminated.

- You must use a "regulated" ("active") terminator with the SS10.

I used an active terminator when the CD-ROM and tape drives were part
of the chain. I don't have a Centronics active terminator to test just
the external HDs. The supplier is sending me one to test this.

- An SS10 has a FastSCSI bus which can only be about 2 meters long.
I think you are pushing the limits of your SCSI bus.

If 2 meters is the limit, I am beyond pushing the limits of the SCSI bus
and would explain my problems. The problem is that it used to work
with total cable length well over 2 meters before (see note to next

- All SCSI chains have limits on the total cabling length and number of boxes
(not necessarily the number of devices) in the chain.

One thing I did not mention on my original message: the two new disks are
replacing one of those duplex boxes (two hard disks in one box). I'm
using the same target # from the old disks on the new disks.. The
difference is that I need an extra cable to connect my two new disks,
while before the duplex box needed only one cable going in and one going
out for both disks.

Does anybody know about a limitation in the number of boxes in a chain?
It would explain why things were working before.

I promise I will send a second SUMMARY as soon as I do some of the other
tests and find the answer to this. I will be away from my office for the
next ten days. I will try to keep up with my e-mail though.

Merry Christmas and a Happy New Year to all,

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