Multiple UPS's - Questions regarding "Shutdown when runtime remaining drops below 10 minute"

[Anonymous user]

I am in the process of setting up Powerchute on your network.  I have something to think about though and I am not quite sure the best way to deal with it...

We have 6 UPS's, all which have different loads and different estimated 'runtime remaining'.  I will try to explain my concern.......

UPS1 which our network switch stack is plugged into has 30 minutes remaining.  

UPS2 which one of our servers is plugged into has 50 minutes remaining.

My plan was to configure PowerChute to shutdown the server when "Runtime remaining below threshold = 10 minutes". However, If I were to configure this it would mean that the switches on UPS1 would have lost all power whilst UPS2 still had 20 minutes of runtime remaining.

As the switches have now lost all power/battery, Powerchute would not be able to communicate between the UPS2 and the server and would not be able to issue the shutdown command.

Is this correct?

[BillP · Accepted solution]

Mike,

On 9/25/2015 7:33 AM, Mike said:

As the switches have now lost all power/battery, Powerchute would not be able to communicate between the UPS2 and the server and would not be able to issue the shutdown command.

Is this correct?

Yes. If the network is down the NMC/UPS would not be able to communicate with the server running PowerChute. You can configure PowerChute to start a shutdown in the event of lost communication with the NMC. So if UPS 1 drops after being on battery for 30 minutes and UPS 2 has 50 minutes of runtime you could configure PowerChute to start a shutdown 8 minutes after communications is lost.

NOTE: There is a 2 minutes buffer for communications lost. PowerChute will wait up to 2 minutes before recording and or reacting to communications lost.

I personally would not do that but it can be done. My reasoning is there is no way for PowerChute to know that UPS 1 actually shutdown after being in battery for 30 minutes and that once communication is lost with UPS 2 PowerChute has no way of knowing that the battery/s on UPS 2 can continue to run for another 20 minutes.

What I would do is configure PowerChute to start a shutdown after communications is lost for 5 minutes and assuming the server takes less than 7 minutes to power down configure NMC/UPS 2 with a low battery threshold of 12 minutes. If UPS 1 has powered off after 30 minutes on battery and UPS 2 then has 20 minutes of runtime PowerChute will start a shutdown when there is 13 minutes left of battery on UPS 2. I am adding a few minutes as buffer for safety.

The reason for this is, if UPS 1 powers off when UPS 2 has 17 minutes of battery life left not 20 minutes a shutdown will begin when there is 10 minutes of battery life left on UPS 2.  Or if UPS 1 runs longer than 30 minutes and UPS 2 has less than 50 minutes of available runtime a shutdown will be started at 12 left of battery on UPS 2 due to low battery. Again, adding a few minutes as a buffer.

The safest option is to put the switch that the server is plugged into on the same UPS as the server.

[Anonymous user]

Yes, that would be ideal.

The complications come into place when in reality I have about 6 UPS's all with different runtimes and different things plugged into.  Some of which are impossible to trace as the previous IT team were not particularly thoughtful with theier cabling!

I wil have to have a think about the best way to do this, I am a little bit concerened about triggering a shutdown when communication is lost as there have been a couple of incidents in the recent past when the UPS's were complaining about communication problems due to an unrealted problem (e.g a change in DNS/default gateway/problem with the time etc). i dont want to risk shutting down the servers unless there is a genuine loss of power.

Thanks for your help, I will have a think.