From: utzoo!decvax!ittvax!tpdcvax!bobvan
Newsgroups: net.unix-wizards
Title: Re: Time of year for kernel changes
Article-I.D.: tpdcvax.192
Posted: Fri Oct 29 22:01:20 1982
Received: Sat Oct 30 05:18:57 1982

Alan Watt's suggestions are good ones that I must admit I hadn't
thought of.  However, we would have a hard time making the program run
by /etc/rc smart enough.  It could easily get our regular weekday
morning down time confused with VMS time and set the clock back when it
shouldn't.

We go down weekday mornings from 5:30 to 7:00 to avoid power line
glitches.  A power line monitor has shown 200+ volt spikes on our 115
volt lines.  There must be some large industrial users near us that
kick in their big machines about that time of day.  Another theory is
that the power company switches in big caps to compensate for the large
inductive loads that are about to hit the lines.

Our VAX 780 is pretty good about ignoring these spikes, but sometimes
they cause mysterious disk write errors and that does who knows what to
our filesystems.  Nobody wants to use the machine in that time period,
so we just halt it.

I can't believe that these spikes are very good for the circuitry
inside the VAX.  We've yelled loudly at the local power company
(Comical Edison) and they have yet to do anything about it.  This site
will be moving soon so we haven't bothered to buy a UPS or a filtering
system.  Have any other sites had problems with spikes at the same time
every weekday?

The gist of this is that the program would have to take into account
the (possibly offset) time of day as well as the staleness of a
filesystem to determine if VMS had run.  Alan's scheme would have
preserved the purity of the kernel, but would have involved changing
more existing code and writing more new code.  If Alan's scheme had
occurred to me, I would have had a hard time choosing.  Shortness of
time probably would have lead me to sacrifice kernel purity, though.
What would you have done?

				Bob Van Valzah
				(...!decvax!ittvax!tpdcvax!bobvan)