[Info-vax] Unpleasant Disk Shadowing Surprise

[abrsvc]

On Oct 11, 10:53 am, tadamsmar <tadams... at yahoo.com> wrote:
> This is VMS 7.3-2 on a DS10.  I am at V19.0 on patch updates (applied
> in July 2009)
>
> Our real-time application halted for more than 3 minutes.
>
> After the incident I found here was a disk error on one member of the
> shadow set.
>
> The first indication was whe the application watchdog alarm went off.
>
> According to the console log, more than 30 seconds after the watchdog
> sounded, the shadow set changed state, the offending disk went
> offline, a mount verification started and completed.
>
> Immediately after the mount verification completed, VMS started
> working again.
>
> Looks like the disk system was inaccessible for about 3 minutes and
> any process that tried to use it got
> halted somehow.
>
> Is this to be expected?  We have had VMS and disk shadowing running
> the application for 20 years or so, but I don't know that we have ever
> had a disk error while the watchdog was configured to sound, so we
> might not have noticed the halting and recovery.

Something sounds a bit fishy here.  Unless the entire shadowset went
offline, there should not have been any interruption.  You may see a
slight performance hit with one member rather than 2, but even that
should be minimal.  Something else was happening here.  Can you
determine whether or not the entire shadowset went offline?

Dan