[Info-vax] Unpleasant Disk Shadowing Surprise

[tadamsmar]

On Oct 12, 6:40 am, VAXman-  @SendSpamHere.ORG wrote:
> In article <168e7442-2c78-4dda-8942-6f831d954... at d28g2000vby.googlegroups.com>, tadamsmar <tadams... at yahoo.com> writes:
>
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> >On Oct 11, 4:16=A0pm, 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. =A0Errors
> >> 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. =A0A single "bad"
> >> error on the one disk can hang the whole bus...
>
> >> =A0 =A0 -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.
>
> Where in the world are you that you have cable eating ozone levels?
>

It's a research center with lots of labs.  It has a single pass air
handling system.  Whereas most offices and homes have a recirculation
system.

Ozone get created in sunlight and it reacts away pretty quickly so a
typical home or office has a very low level of ozone inside.  A
building with a single pass system has ozone levels pretty close to
the levels outside the building.

I had to replace one god awful looking SCSI cable with obvious exposed
copper wires.  There is a general belief here that ozone is a problem
for all sorts of components in our building, but I am not an expert on
the matter.

> --
> VAXman- A Bored Certified VMS Kernel Mode Hacker    VAXman(at)TMESIS(dot)ORG
>
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