[Nut-upsuser] ordered shutdown

[Marco Chiappero]

Arjen de Korte ha scritto:
> If you want to conserve power on your UPS, you should simply send a  
> client a command to shutdown.

How can I do that? How can I shutdown different systems at different 
battery charge levels (or expected runtime)? I thought the only option 
aviable was using upssched.

> You *will* need programmable outlets if you need to restart/reboot  
> part of loads attached to a UPS. That comes in handy if you want to  
> shutdown some servers earlier than others, to prevent that your only  
> option is to power cycle *all* loads to make them start again if the  
> power returns before the battery is empty.

Right.

> We're currently working on implementing this and already have made  
> some progress in that direction (see the latest nut-2.4.0 release  
> where a repeater mode was added) so you can have 'virtual' UPS  
> devices. Basically what is lacking right now, is tying these virtual  
> devices to UPS outlets and a way to configure the shutdown/restart  
> levels for these outlets. We have some ideas on how to do that, but it  
> is currently lacking development time to implement this.

Ok, thanks, I missed these news! Hoping for some other soon :)

>> In my opinion that's a limitation and, again in my humble opinion, poor
>> design. It sounds like refuelling a car on a $TIME schedule rather than
>> an avaiability basis: I use to refuel when the *real* remaining fuel is
>> below a certain value/charge, do you use to refuel on a *supposed* fuel
>> consumption over $TIME?
> 
> This is actually how battery charge calculation works on a UPS,  
> strange as it may seem. Most (if not all) batteries don't come with  
> fuel gauges like your car, so all but the cheapest UPS systems will  
> constantly keep track on how much charge is going in an out of the  
> battery to calculate the charge in the battery.

I'm sorry, I didn't state explicitly I was talking about upssched. I 
prefer to choose when to shutdown the computers looking at the battery 
charge or the remaining runtime rather than after X time. In the same 
way I use to refuel looking at the remaining fuel or expected range 
rather than, let's say, once a week because I suppose it's necessary not 
to suddenly stop the car. This is what I was trying to say, referring to 
the scenario described above.

> Having said that, you should *always* take into account that the  
> battery capacity may be less than expected (calculated) due to aging  
> batteries, so you can never fully rely on the reported battery.charge  
> and battery.runtime. If you search the archives, you'll find plenty of  
> examples where people found this out the hard way. This is one reason  
> why one should periodically run battery tests to find hidden battery  
> problems that only surface under load.

You are right, but this is another story. Some room is always needed 
above the method used (runtime, battery charge or time from outage).

Thank you for your reply.

Best regards,
Marco Chiappero