[Info-vax] Unpleasant Disk Shadowing Surprise

[tadamsmar]

On Oct 12, 12:02 pm, Kenneth Fairfield <ken.fairfi... at gmail.com>
wrote:
> On Wednesday, October 12, 2011 1:11:42 AM UTC-7, tadamsmar wrote:
>
> [...]> I looked at SHOW DEVICE DK.  I now see that I did not read it
> > correctly earlier, and I have been confused about some things.
>
> > The real sequence of events is that DKA100 went offline and DKA0
> > logged an error at almost exactly the same time! Those are my shadow
> > set. Hopefully that was a soft error on DKA0 so that my data is not
> > compromised, I need to double check that.
>
> > I rebooted just before I left work and DKA100 did not even show up
> > after the reboot.
>
> > I am now thinking that I probably have a bad SCSI cable.  I will
> > replace that tomorrow, I think I have one in storage.
>
> [...]
>
> I find your error analysis logic, hmmm, "unusual".
>
> The first event was that DKA100 went offline.  The
> second was that it didn't show up on reboot.  I'd
> call that a bad disk.  
>
> Why (in the world) do you jump to the conclusion that
> it's the SCSI cable???  You do understand that the same
> cable is used to access DKA0 as DKA100, and if there
> were a problem with the cable, you probably wouldn't
> be able to boot at all (or at least, without errors)
> off DKA0?
>
> Go replace DKA100 and get on with your life. :-)
>
>    -Ken

I don't see how a failure of DKA100 could have caused
an error to be logged on DKA0.  Please explain your
reasoning.