[Nut-upsuser] ordered shutdown
Arjen de Korte
nut+users at de-korte.org
Sun Feb 15 10:58:21 UTC 2009
Citeren Marco Chiappero <marco op absence.it>:
> Well, right, but PSP it's not intended for network use, while NUT indeed
> it is. I took it as example for showing the above reason and how easy is
> to choose from different criteria in a standalone environment:
You hit the nail on the head. While it is fairly easy to change
shutdown parameters in a standalone application, this is not so easy
in a networked environment. In a standalone application, you can rest
assured that once the shutdown condition has been reached, the system
*will* go down and recovering from that is fairly straightforward too
(since this will be dealt with by the UPS itself). No need to deal
with transient conditions.
In a networked environment with multiple shutdown levels, you'll also
have to deal with transient conditions and also with the situation
where the power returns between two levels (and how to recover from
that) and making this system fail safe too. This is vastly more
difficult to handle.
> If I'm not wrong it should be pretty easy to set up ordered shutdown
> with different criteria in apcupsd too. Me and some other people
> reported that actually NUT can't easily cope with similar requests. Is
> there something more to comment on that?
Yes, there is. If extending runtime by shutting down loads is
essential to you, chances are that what you really need is a generator.
Most of the power outages you'll experience in everyday life will be
short lived (in the order of seconds, mainly due to switching
operation in the grid), which are corrected automatically. This is
something that can dealt with easily with the runtime of basically any
UPS in existance.
Longer outages are usually mean that something is broken that can't be
corrected automatically and/or requiring human
intervention/replacement of systems. This means that the outage will
be much longer than the runtime of UPS batteries. No matter how much
load you're shedding. Even at no load, most UPS systems won't hold up
longer than about 45 to 60 minutes. If you've already used up part of
the juice, it will be even less. So you're systems *are* going down in
If losing (some) systems is really a big deal to you, having a UPS is
only part of the solution. Personally, I feel the option to shutdown
part of the loads depending on battery charge or runtime remaining is
largely a waste of effort. You'll still have to deal with the
situation where the battery state triggers shutdown on all systems at
the same time (after recovering from an outage, followed by another
outage for instance).
> So, I'll keep waiting for the features. :-)
...instead of working toward a solution. You see where the root of
this problem lies? The active developers don't have this high on their
list of features and the people that want this, don't provide any help
in adding them.
Don't hold your breath waiting. ;-)
Best regards, Arjen
Please keep list traffic on the list
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