Correct size UPS for Dell t410

SM17CH used Ask the Experts™
Im trying work out the best size  UPS for our servers. (without going over board and over priced)

We have -
1 x Dell t300 (Single quad core processor, 2x SAS drives, two power supplies)
1 x Dell t410 (Dual quard core processor, 2 SATA drives, two power supplies)

How do I correctly detirmine what I need?

Servers only need to run for 10 minutes in a blackout so they have enough time to safely shutdown.

Each server would need to connect to USB on UPS so it can get the shut down signal. Does this mean I need a seperate UPS for each?


PS; the APC website has a UPS sizing application. It told me I need 1 2200VA UPS. This seems overkill to me as it says only 48% capacity on the UPS will be used allowing the servers to run for 27 minutes.
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A 2200VA UPS will require 15 amp power (here in Australia, anyway).. lower than that and you will need only 10amp. It strongly depends on the kind of load that your servers are under as well, CPU's running hot will suck more juice than something at idle.

I just sold a T410 and provided the customer with a APC 1500VA Back-UPS RS, which will be used on both the T410 and a HP DL320 g5p. I would recommend the 1500VA Smart-UPS over the Back-UPS. We only went with the Back-UPS as the client has a tight budget.

Back-UPS RS:

Smart-UPS 1500VA:

At 500 watts load you'll get approx 26 minutes; which leaves plenty of overhead as the unit will do 980w at full load.
Also, I have found the bundled APC "Powerchute" software to be of inadequate quality, as it always seems to lose connection to the UPS and whatnot.. their paid versions might be better and allow shutdown of multiple systems. The bundled version only allows shutdown of the attached system (when it works).

You can however create scripts to shutdown the other server.
Thirdly.. it doesn't hurt to have two UPS, especially as both servers are dual PSU. Plug one UPS into one PSU on each server, and the other UPS into the other PSU's.  This means if the UPS fails, then the other UPS is still available to provide power to the servers.

By doubling UPS's you can't reduce the UPS rating, so you'd still need around 1500VA for both UPS in case one UPS goes offline and both servers start to draw from the single unit.

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thats great info thanks alot. im in Australia also so even more relvant.
I just want to confirm that you think 1x 1500VA will run both servers for 20ish minutes?

Depends on the conditions of the batteries.. but you should get around 10 to 15 minutes easily if they are at low load. If they can afford a 2200VA and required power works (any electrician can add a 15 amp outlet easily), go for that, if not, a 1500VA will suffice.. or maybe a 1500VA with extended runtime (same output, but more batteries).
If this is your first UPS, I would recommend buying two.  Each one should be sized for one server +25-100% depending on your future expansion needs.

With two UPS, you'll get USB hookup to each server without buying additional network card or installing a server+client software package to perform multiple shutdowns.

Another big advantage, since you have redundant power supplies on the servers, is plugging one PSU into each UPS.  If you lose one UPS (or have to move/reconfigure), you'll always have one PSU powered up.

I discovered this shortcoming when I needed to untangle a rat's nest of cables that had accumulated over a few years.  The ability to unplug the PSU and move them around was a great help.

The t410 has 2x 580W supplies (one redundant).
The t300 has 2x 528W supplies (one redundant).

So, max load you'll have is less than 600W or ~840VA when adjusted with a 0.7 power factor.

An SU1000 (1000VA) unit would give you 8 minutes at 600W (the max draw from one of your servers.  That would only be at startup with all fans and drives running full speed.  But, you need to know your environment.  During normal running, you may only draw 50% of your max power rating.

But, if you're having power issues, you may have already lost HVAC to your office, and environmental temps may climb to 100F+ in a short period of time.  In one closet I maintained, it took less than 10 minutes after loss of air for the temp to climb from 72F to 105F.  During a power incident, HVAC motors may shut off for safety.  This leaves your servers running with intermittent trips of the UPS.  As the temp rises, more fans will kick on, increasing load.  Planning for 50% as your normal running load may give you significantly less time during an actual power incident.

You also have to plan for startup.  If you don't have the amps to handle startup, you may trip the UPS to an "off" state.  It's a safety that prevent you from drawing more power than the equipment is rated for.

As a minimum, I'd get 2x 1000VA units.  If the budget prohibits two units, then 1x 1500VA unit should still have the ability to handle startup of both servers simultaneously, but may have less runtime during a power incident.

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