[Info-vax] Unpleasant Disk Shadowing Surprise

[Kenneth Fairfield]

On Wednesday, October 12, 2011 10:09:20 AM UTC-7, tadamsmar wrote:
> On Oct 12, 12:02 pm, Kenneth Fairfield <ken.fa... 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.

OK, this is getting ridiculous: "You show me yours, then
I'll show you mine" ???  You didn't answer my question.
Nor VAXman's earlier in this thread.  Sigh...

For one thing, you write a lot of prose but show almost
no actual evidence, as in a cut-n-paste of SHOW ERROR,
SHOW DEVICE DKA, or the output of ANAL/ERROR.  It's all
descriptive and imprecise.

This is the first I recall in this lengthy thread
(granted I could easily have missed it) that you've 
mentioned an error on DKA0.  OTOH, you *have* rebooted
the system since the disk failure so anything logged
against DKA0 now is most likely unrelated to the 
initial failure.  Is the bad disk (DKA100) still on
the bus?

I will note that with HSG-hosted disks ($1$DGA), ISTRC
that every mount generates one error count in SHOW
DEVICE agaist the disk being mounted.  I don't recall 
that for directly attach SCSI disks, but I have far 
less access to VMS systems now than even a year ago. :-(

The only way you'll have a clue whether the error logged
against DKA0 is significant is to get the full output from
(the current incarnation of) ANAL/ERROR for that disk.

   -Ken