I’m trying to decide which UPS to get for my server. Currently, my server idles at around 35W and reaches close to 50W under load. I’m planning to add two more HDDs, which might increase power consumption by approximately 20W in the near future.
I had almost decided on an Eaton 5SC 500i (350W/500VA), which in my mind would leave plenty of capacity even after adding the two new drives.
However, I recently read a blog post claiming that a server’s electricity needs peak during startup, and that you should account for this as well. My server has a Be Quiet Pure Power 12 M 550W PSU.
Do I need a bigger UPS, or will the 5SC 500i be sufficient?
I would ALWAYS go for a model that has sufficient room for expansion. What about switches, broadband/DSL/modem, monitor?
It also helps to write down the scenarios to be covered. E.g. should the server start again, once the battery has been recharged to a sufficient level?
There’s another very important aspect to this. Is the UPS compatible with the NUT subsystem so that it can shut down the NAS in an orderly fashion and be monitored?
Eaton have been progressively switching to proprietary protocols which prevent them being used on Linux/FreeBSD platforms.
All other equipment is covered by surge protectors and doesn’t need power backup.
I want the UPS for data protection, so a clean shutdown if the power goes out.
If the server can be turned on automatically when the power is back, that’s a nice bonus but not needed. No critical services or shares will be hosted on this machine.
I’m so new to this that I don’t what other scenarios are even possible to cover with an UPS.
I’ve heard mixed reviews of the Eaton UPSs, but if you have trustworthy recommendations for that specific device, then it’s probably a good choice.
I run my NAS with an 800VA UPS from Powerwalker.
For electronics which is permanently under load, I prefer to over-size rather than just meet the requirements as it will run cooler and last longer.
My previous UPS lasted about ten years, with one battery replacement during that time.
Beware of the “GreenCell” UPSs that you might find on Amazon. The supposedly “green” batteries that they use are rubbish.
True sine wave is nice, but not essential in this application as the switched mode power supply in the computer will first rectify the incoming AC to DC before converting it to the lower voltages needed by the computer.
A pseudo sine wave might cause the diode bridge in the PSU to run a bit hotter than normal, but these components tend to be over-specified in a good quality PSU and it doesn’t cause a problem.
Hi, you can make sure yourself by simply measuring power consumption in different phases of operation with a simple watt/power meter. If you don’t have one at hand lets do some theory:
Be Quiet Pure Power 12 M 550W PSU can supply up to 550W to hardware, which means that must not happen. Judging from what you wrote (50W load)… that is unlikely. Mybe you want to share hardware specs?
Usually UPS can handle short peaks that go higher than what they are rated for. Unfortunately Eaton does not provide info about max. peak load for that model.
Boot phase with HDDs spinning up is probably the most demanding phase. Even with 4 HDDs spinning up simultanously … your server will never even get close to 200W peak.
That Eaton 5SC 500i (350W/500VA) is surely enough.
The other side of the coin is about how long you want the UPS to be able to continue to power the load after the mains goes down.
You need, at a minimum, enough reserve power to keep the NAS running while it executes an orderly shutdown. The smaller the VA rating of the UPS, the fewer minutes you have available.
While the statement is absolutely correct, some might misread it. I am looking at the term “unlikely” here. In other words: There are situations where you might still have a problem.
Two reasons:
The 50 W load is under normal operation. In other words, during startup the load will be higher. A hard disk with 10-12 W power draw during active operation, can require 30-40 W peak during startup. For my system with a power consumption between 100 and 200 W during normal operation, a 500 W PSU was not enough for startup.
The 500 W is the combined power. A final statement requires understanding about which voltages require which power on the consuming side, and how the PSU delivers its overall power across the various voltages and rails.
So the reports in various forums about UPS + PSU combos that don’t work nicely together is rare outliers that one can presume you won’t run into?
When I continued to research this yesterday, some discussions hinted at what @ChrisRJ brings up: That it was the PSU’s power draw during startup was bigger than what the UPS can provide that causes the problem.
According to my PSU’s data sheet, while rated as 550W, it’s peak power is 600W.
So perhaps it’s more important for me to get a UPS at 600W or more, but not necessarily with true sine output?
Ah sorry, your server is probably permamently drawing power over that Eaton 5SC 500i (350W/500VA). In this case boot phase is relevant for this Line-Interactive UPS since power always runs over Transformer “AVR”:
