I'm adding more servers here at work, so I want to get a new UPS. I'm not sure how to shop for one though? Do I add up the wattage of all the Power supplies to determine the minimum I need? Do I need to worry about VA Ratings, and if so how should I determine my needs?

I plan on hooking up 4 servers (1 Dual-Xeon, 1 Dual-core Opteron, 2 X2's), plus an LCD (just 17" most likely).

I'm mostly concerned with preventing the machines from resetting during power surges (which our area is prone to), rather than keeping them up for hours during a blackout. I don't want to skimp, but I also don't want to buy a $1k UPS if it's going to be overkill.

Thanks in advance

I really like APC's stuff they are not overly expensive. With a 350VA you can look at 8 to 15 mins of run time depending on the system specs. The more things you can limit off of it the longer it will run. 500Va roughly 10 - 20 mins again depending on your setup sometimes you can get more or less, but these are common times for myself.

For Example at home I have 3 of them for my main rigs, and I only plug in the tower and the monitor speakers and printers and stuff is plugged into a powerbar. Now if I need something during a power outage I can just plug it into the UPS.

Well if you're looking for some points of reference, I picked up a Belkin 1500VA a while back (with the old 1/2 off coupon code), and it's been really great. I have had the power go out a few times since and by watching the battery levels for a bit before shutting down, I figured I'd get about 15 minutes of relatively idle battery time with my system. That's the PC, cable modem, router, and my old 22" CRT.

So anyways, it could probably support two of those systems, but I don't know if I'd put them all on it. Mainly because most UPS's will shut down completely if you overdraw them (mine did when I tried to turn on two big 22" CRTS at the same time, both through the UPS). So if you overload it, you could easily cause more outages than you prevent.

Really wow, I have had two systems plug in, with two 19" LCD's and never had issues and I do that alot. Was this with your big Belkin one or a smaller one?

It was the 1500VA Belkin. But the problem isn't the working "load", it's the power-up "load". A CRT draws a big power spike when it starts up. In this case, I had two big CRTs plugged in to the UPS and I turned them both on at the same time. The spikes were enough to overdraw and the whole thing powered down to "protect" it. So effectively, my outage-stopping UPS is what caused my outtage

Anyways, I just took one of the CRTs off it and it was fine. Plus, now I have an LCD which draws less power and doesn't spike nearly as hard on startup. I ran the 1500VA for a long time with two A64 systems and one big CRT and I never had problems. But with one system burning a DVD and the other playing WoW, I'd hit 70-80% load on the UPS. So if they were "critical" systems, I'd be worried about being that close on 24/7 usage.

My initial thought was to say that two 1500VA-ish units would be enough, but I really don't know enough about server power usage to say that for sure. Plus, it depends on what kind of regular loads they'll see. It might not hurt to pick just one up and do some load research, then go from there.

i own a 15000 back up for my computer and tv its pretty big i got off a guy running some school severs off of it i like it it has come in handy alot.

Ahhh ok that makes sense gotta love CRT's

Thanks guys, your info is really helpful so far. But I noticed that neither of you mentioned wattage. Is that not as important as the VA Rating? One UPS system would have made monitoring easier, but if going with 2 would be safer, I'd obviously choose safety/reliability over ease of use. heh.

But yeah, so what about wattage? Let's say each system theoretically has a 500W PSU....so 500W x 4 = 2kw...would that mean I need a 2kw UPS, or am I totally missing the mark here?

Here's what I know:

VA stands for Volt-Amp.

Wattage is calculated by multiplying Voltage by Amps consumed.

So if we take a slight venture and assume Volt-Amp = Volt * Amp, then VA = W. But then why do most UPS's list VA and Watts as different figures? RMS translations, perhps?

Anyways, I guess the short answer would be "I don't know" Unfortunately Belkin's site doesn't seem to list a wattage rating for mine, so I can't really compare.

I recently tested my PC and it draws an absolute max of about 320W from the wall. Relative to that, I'd guess the secondary rig I had on at the time would be a max of about 220W. I looked up the rating for my big CRT at one point, and it was about 110W. I'd guess another 40W or so for cable modem, router, etc. That's roughly 700W which put my 1500VA at about 75-80% load max. So that would put 100% load of the UPS in the ballpark of 935W AC.

Anyways, take whatever you want from that, I guess I'd think the best move might be to get one good sized UPS and then test it on the different systems to see what kind of loads you get, then add other UPSs accordingly. My biggest concern would just be running them too close to 100% all the time. It would really suck to have the UPS switch off if usages bumped up a bit.

Yeah - you're missing the mark

The 500W PSU represents maximum DC power output from the PSU - not how much power you'll draw from the mains. So unless you're running your severs at full load of the PSU you don't need anywhere near 4x500W.

Next, I would run each server on it's own UPS if it were me to avoid the situation Verran mentioned above about overloading the UPS as well as being able to use the included software to shutdown each server independently during an extended power outage if needed.

Now, I have the following UPS backing up a dual Opteron 250 server running a 550W PSU:
APC Back-UPS XS 1500 UPS, 1500VA, 865watts with BR24BP Battery Pack. I don't plug my CRT into it and it once kept my server running during a 45-60 minute power outage. According to the software, I was using about 265 watts. You can get a single battery version of this UPS for about $100 less.

Another alternative might be to hook up one server and one X2 to each UPS and get by with 2 UPS units.

Most UPS vendor sites have some sort of calculator/selector option on their web site to help you choose.

It's to do with the differences of the load being a purely resistive load, which should just simply follow ohms law (thus VA would be equal to W) and a load which is not just pure resistance, but also exhibits capacitance or inductance.


I think

I got a cheap one in 05 and one day i unplugged my laptop from it...as soon as i did smoke came out of the plug. i unplugged it and threw it in the snow. 50 bucks wasted...could have killed me...GURRRRRR

I have never used one but have thought about getting one myself. @ coolcat97, you get what you pay for....

If i didn't catch it and it burned my house down, could i have gotten the "$250,000 Dollar Equipment Guarantee" or whatever?

I think we may try this 3000 VA 2850 Watts one. We're going to discuss it more on Monday, but that should be able to house all four of our servers. It'll probably give us around 7 mins of backup time at full load, which is fine because again, we're just concerned mostly about surges and brownouts, not holding up over an extended blackout (when every client pc is down, it won't matter much if the servers are up).

The only APC I used is old, so the software is probably different now, but I know you're usually able to set actions/scripts depending on the amount of time it's on battery, so I'd just set them to shutdown after a minute or two of battery, depending on what the load readings are giving me. So I think this will suffice...plus is rackmountable, in case we move the servers onto a rack, though we just built a fancy desk from scratch, so I doubt it

Thanks again guys

You are aware that a UPS of that size doesn't simply plug into a wall outlet, right? I assume that from your post this isn't in a server room with dedicated wiring?
It takes a special socket and I am not sure what the minimum amp service you need:


You'll notice you will need to run a dedicated line if you don't already have it.

No, I didn't notice that, thanks for pointing it out. I think I'll call APC on Monday and ask them about that. Because I looked online and couldn't find any wires that had NEMA L5-30P connections on both ends, and I know a cable is included in the package, so I'm wondering exactly what I need to connect it.

That's the type of socket/outlet from the mains - i.e. the wall outlet. You'd have to have an electrician run a drop to wherever this is going to be located. I am fairly certain that requires a 30-amp circuit, hence the special plug.

EDIT: A picture's worth a thousand words so I put my uber MS Paint skills to the ultimate test:

good idea staying with APC. while the others may be just as reliable... APC stands behind thier insurance claims MUCH better.



also make sure you're replacing the batteries in that thing every 12 - 18 months.

Alright, thanks guys. I'll let you know how the discussion goes on Monday

...change batteries every 12-18 months? the one we currently have hasn't been changed since I've gotten there and I've been there 20 months...and who knows how when it was purchased. Like I said though, we don't care about sustaining the servers over time, and it still did its job during those quick brownouts.

See bigred's post here. That post was certainly and eye-opener for me.

thanks, must have missed that thread. I'll make sure we replace the batteries in the new one(s) we get on a regular schedule.