[Info-vax] Unpleasant Disk Shadowing Surprise

[tadamsmar]

On Oct 11, 4:16 pm, Kenneth Fairfield <ken.fairfi... at gmail.com> wrote:
> On Tuesday, October 11, 2011 11:53:12 AM UTC-7, tadamsmar wrote:
>
> [...]
>
> > Here is what I find in the error log:
>
> > I had two errors on the pka0: (adaptec aic-7899) at times 7:58:14 and
> > 7:58:21
>
> I was more interested in what SHOW DEVICE DK shows
> for the members of the shadow set in question.  Errors
> on the PK device are not terribly interesting most of
> the time (they tend to come in ones and twos at boot
> time, etc.).
>
> Of course once you've done a dismount on bad disk,
> the count gets reset.
>
> But as others have noted, having both shadow members
> on the same scsi bus is problematic.  A single "bad"
> error on the one disk can hang the whole bus...
>
>     -Ken

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.

We have a single pass HVAC system in our building so the ozone levels
are close to outdoor levels and this tends to eat the insulation on
cables.