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Re: ARGH, weird SCSI I/O errors on second/third drive on Debian/PPC

On  27 Dec, this message from Jessica Blank echoed through cyberspace:
> On Fri, 27 Dec 2002, Michael D. Crawford wrote:
>> Could the original drive still be terminated after you have installed the other 
>> drives?  It is probably worse to have extra termination than to have none at 
>> all.  Make sure you've got it right.
> The original drive was NOT installed at the end of the chain. (The 
> original Apple-branded CD-ROM drive was...) So I don't think termination 
> would be an issue for this drive, no?

How did you install two more drives in the 7300? Did you remove the

Anyway, your SCSI chain needs to _physically_ look like this:

  Host--------------------------------------------last device
        |         |         |         .....|
      Device    Device    Device         Device

Only the last device must have termination, none of the others must have
(well, the Host does, but that's automatic).

So, verify your SCSI cabling in the first place. All other devices
except the physically last one (i.e. at the end of the flat cable) need
to have termination switched off. Verify that with the help of the
manufacterer's jumper info.

Then, you can try to use another drive providing termination, in case
that specific drive has problems with its termination. That means
physically rearranging drives.

> How do I know if I got it right? I wish there was a "scsidiag" program 
> that would say "Your termination sucks, try this; your SCSI IDs have a 
> conflict, try this..."

There is no other way than to open the case and have a look, sorry...

> The thing that confuses me is thus: There are several termination options 
> for the drive I placed at the end of the SCSI chain (read the Web page I 
> referred to: http://www.seagate.com/support/disc/scsi/st15150n.html ). I 
> do not know which ones are  correct. "Terminate power from drive"? 
> "Terminate power to SCSI bus"? I know nothing of these things.

Ah, Seagate. They have a jumper to enable termination: that is putting
'the plug on the cable'. This 'plug' needs power, and the other jumpers
specify where this power comes from. 'Term power from drive' uses the
driv'es power for this. 'Term power to bus' is independant of the
on-board terminator; it serves to provide termination power to the
reserved wire in the SCSI cable.

But, there is something else you need to make sure.

The error messages you describe _may_ indicate that the filesystems you
created are larger than the actual drive. This can happen when
partitioning with some (older?) versions of mac-fdisk (aka pdisk).

Try using badblocks to verify the drives are OK. Or try using 'dd' to
read the entire drive (something like dd if=/dev/sd<x> of=/dev/null
bs=512 count=<number of blocks>).

If this is your problem, you need to specify the correct drive size when
creating a partition map with mac-fdisk.



Michel Lanners                 |  " Read Philosophy.  Study Art.
23, Rue Paul Henkes            |    Ask Questions.  Make Mistakes.
L-1710 Luxembourg              |
email   mlan@cpu.lu            |
http://www.cpu.lu/~mlan        |                     Learn Always. "

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