UPS question

[Koldov]

Think I'm confusing myself here with too many scenarios...

 

I have 2 servers (each with 2 PSU) and two UPS.

 

 

For SVR 1, I have:

 

PSU 1 - plugged into the wall

PSU 2 - plugged in to UPS 1

 

USB for Powerchute between SVR 1 and UPS 1

 

For SVR 2, I have:

 

PSU 1 - plugged into the wall

PSU 2 - plugged in to UPS 2

 

USB for Powerchute between SVR 2 and UPS 2

 

Somewhere in the back of my mind, I have the idea that actually the servers shouldn't even be plugged in to the wall and in fact the 2nd PSU should be plugged in to the opposite UPS.

 

 

I've talked myself out of it before due to the fact that UPS 1 and SVR 2 can't communicate, so for example if UPS 2 dies, theoretically SVR 2 could still get power from UPS 1... but then when UPS 1 dies, it will never tell SVR 2 to shutdown.

 

Thing is SVR 2 would have already been told to shutdown by UPS 2 when it failed... so there's no point in attaching SVR 2 to UPS 1 anyway...?

 

The only point of doing it therefore is just not having them plugged in to the wall, thus benefitting from power conditioning, surge protection etc.

Edited January 7, 2025 by Koldov

[dmj]

You'd normally plug the UPS into a bypass so that you can failover or do maintenance on it.

Don't plug the servers into the wall, you negate all the surge protection. The bypass is designed for this.

https://www.serverroomenvironments.co.uk/apc-smart-ups-vt-maintenance-bypass-panel?gad_source=1

 

edit: I linked to a manual bypass, but you should have an automatic one incase of failure.

Edited January 7, 2025 by dmj

[PotNoodleTech]

Yep the second picture is the one you want as it fully protects from surges and sags.

 

Try and make sure that both UPS's are big enough to handle being able to power both servers on just one of the UPS's - just incase a UPS goes down or like you say you need to do maintenance.

 

If you underspec the UPSs you will go through/damage batteries and during power cuts you'll only have 10 minutes grace. If you overspec the UPS's the batteries last much much longer, mine are over 6 years old now original batterys no swelling and still 1 hour of runtime.

[DalekSec]

2nd one,

 

Even better if you can get both UPS's on seperate ring mains but obviously depends on your local electric!

[dmj]

2nd one,

 

Even better if you can get both UPS's on seperate ring mains but obviously depends on your local electric!

 

Ideally, it would be on three phase

[Koldov]

Thanks, I think I knew deep down it was the second option... I'll swap it all over ASAP, just for the protection!

 

Not overly concerned with the runtime I guess, just as long as it's enough to do a graceful shutdown.

 

I'm still not sure about that anyway, as I said I believe that SVR 1 would shutdown when UPS 1 gives up and SVR 2 will shut down when UPS 2 dies as it's set to send that communication through Powerchute, so in theory one UPS will never actually 'run' two servers.

 

Thing is linking them both together like that, if UPS 1 actually dies (not low battery) and both servers then run from UPS 2, when UPS 2 gets to a low battery, SVR 1 will never get the communication to shut down...?

Edited January 7, 2025 by Koldov

[dmj]

 

I'm still not sure about that anyway, as I said I believe that SVR 1 would shutdown when UPS 1 gives up and SVR 2 will shut down when UPS 2 dies as it's set to send that communication through Powerchute, so in theory one UPS will never actually 'run' two servers.

 

Just get the bypass and keep it all running IMO.

[DalekSec]

Ideally, it would be on three phase

 

True but i was going by the pictures on the diagram not being a higher capacity UPS setup and normal plugs.

[PotNoodleTech]

Even if it's not three phase taking a second feed for UPS 2 from a seperate consumer unit in the building is a good idea as it will increase uptime as if a cleaner plugs a broken vaccum in outside the server room and trips the whole consumer unit out (happens!) then the other consumer unit the other end of the building will still keep the server room going.

 

Depends on your funding but IMHO well worth a few hundred quid for a leccy to fit an extra cable run.

 

We're three phase so I have one UPS running off one phase (say blue) on one consumer unit and the other running off another phase (say yellow) from a seperare consumer unit so if a UPS fails we stay up, if a consumer units trips we stay up, even if a phase goes down in the enitre school - which has happened, the server room keeps going.

 

The only actual downtime I've ever had that wasn't automatically mitigated by the mutiple ups/multiple phases approach was when Western power installed an entire new substation for us which was unavoidable downtime and secondly when we had a power cut to the entire town - about 20 square miles taken out for 6 hours - again beyond my control.

Edited January 7, 2025 by PotNoodleTech

[Rob_D]

Some years ago I had one UPS on 2 servers and managed to connect one via the USB and the other by the serial port.

 

Or, what about attching both UPSs to one server to monitor, and have it send a remote shutdown command to the other one when PowerChute takes it down?

[dmj]

True but i was going by the pictures on the diagram not being a higher capacity UPS setup and normal plugs.

 

oh yeah, they're teeny. I didn't notice from the picture.

[chazzy2501]

if the UPS is plugged in to a server via USB, then you are doing the correct thing. I'd like the direct mains to have a surge protector. if you run both servers from the both ups one may last longer than the other, the servers may draw more power from one before the other and shutdown earlier than necessary.

 

servers with 2 power supplies can be configured to fail over or load balance... which PSU is plugged into what UPS, servers using what one for failover...

 

1 ups 1 server is real simple and the way to go. (until larger scale installs)

 

BTW my new APC UPS (that I got just recently) appear as a battery icon on the server like a laptop without any stupid software, how cool is that!

 

EDIT: BTW I had a server PSU blow up once and it damaged the other devices connected to the same UPS. (APC SU2000RUI) so the surge protection was only from the mains, not the other devices connected to each other.

Edited January 8, 2025 by chazzy2501