Help me check out UPS spec please?

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  05 May 2013
Help me check out UPS spec please?

Hi everyone. My studio is about to order 2 of this as our render nodes.

There are 8 blades. Each blade would be using Duo Xeon Sandy Bridge 8C E5-2660 2.2G 20M 8GT/s QPI.

At first, our vender offered UPS with 3,500W, 5,000VA.

But later, our vender said that wouldn't be enough and offered us 8,000W, 10K VA which doubled the UPS price.

Any suggestion how much power I should really be going for? In the blade's spec says it'd come with a 1620W power supply.

Thanks in advance!
  05 May 2013
Some quick napkin maths, purely for the cpus (so excluding ram, drives, motherboard, fans etc), youre looking at about 130watts, x2 for each blade, x8 for each enclosure, x2 enclosures = 4160 watts when rendering. Throw in the motherboards and other components and they could be doing a good 6kwatts.
Matthew O'Neill
  05 May 2013
the 2660 actually has a maximum of 95W TDP, the actual draw is hard to spike to 90, and those platforms tend to be efficient.
Each blade should be in the 200W realm, slightly above under pressure with all wheels spinning (assuming they get kitted with local storage and that it's a relatively power hungry spindle 7200 rpm you're willing to cool).

3.5KW actually SHOULD cover two of those enclosures, but if they run at capacity for a long time, or a fault in the PSUs were to kick in the redundant one while the other still drew, you could, however unlikely, get a spike the UPS wouldn't be able to deal with. So 3.5KW is a beggar kind of coverage, and seems slim margin.

8KW however seems largely excessive, it would support a double failure with double full draw for minutes in case it happened in a protracted blackout.
While theoretically possible, is probably slightly less likely than you having to fret about a meteorite strike on your renderfarm (and therefore setting up an anti meteorite laser capable anti air network around the facility).

When dealing with UPS everybody selling errs on the side of caution, both because they want to skin you for all the money they can, and because as you are fundamentally buying insurance, they want to cover their arse and make sure it's full insurance, even in unlikely events.

Last but not least, bigger UPS also have better amperage to the batteries, that means the unit will stay up longer. So it's also possible you guys asked them a minimum time (or they considered one) for the UPS to hold up while you shut down, and the amperage of the 8K unit is needed.

I'd have a chat with them and ask by what parameters they reckon they need to cover well over twice the actual draw, which is a bit of a rule of thumb, but might be overzealous in your case.
Over twice the load with the mains firing on all cylinders for a protracted time seems excessive even when accounting for some multiple draws (redundant units kicking in while anothe burns out). Something in the 5-6KW range would more than cover it, but again, they might have made honest considerations in offering an 8KW unit, or be leaving space for upgrading the CPUs to a higher draw.

3.5K would barely manage but be on the short end of things, and that'd defeat the point of an UPS.
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Last edited by ThE_JacO : 05 May 2013 at 12:49 PM.
  05 May 2013
Thanks everyone. A quick look around APC website I found they have 4000W, and 6000W. I was thinking 5000w would be ideal, but since it's not available, 6000w would be my next choice. It's only a tad lower than 8000W though, I wonder how much cheaper can it get.

How did you figure out the watts needed for each individual blade?
  05 May 2013
A mix of experience and searching in the right places. You should be able to obtain it from your reseller as well, if they are serious about selling the kind of gear we're talking about they SHOULD have tested the actual draw of those enclosures, and not base things on napkin maths.
Come, Join the Cult - Rigging from First Principles
  05 May 2013
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