What is the most accurate tool or mathematical equation to calculate a power supply for unRAID?

 

I'm looking for something that's dynamic.

 

Thank you

anvien

I am not sure how "accurate" this website is but I used it and the results seemed reasonable.

 

http://www.extreme.outervision.com/psucalculatorlite.jsp

 

If you want real world results - get one of these

 

http://www.homedepot.com/p/t/202196386?productId=202196386&storeId=10051&langId=-1&catalogId=10053&ci_src=14110944&ci_sku=202196386&cm_mmc=CJ-_-6146836-_-11210757&AID=11210757&PID=6146836&SID=1npud9pqcyki8&cj=true

Well, I highly doubt that a simple "kill a watt" can tell you the real world that is of interest.

 

Especially in our use case with so many drives, the dimensioning of the PSU is not the

Wattage (which is probably measured very well with the "kill a watt") but the

current (A) drawn at start up.

I can hardly believe that such a cheap tool can measure the transient current

in the first 2-3s during start-up.

Well your probably right. I've never actually used one to be honest. I have to imagine that there is an expensive toy of some sort that would tell you what you wanted to know though... It just might cost more than the power supply!

I'm pretty happy with mine.  I don't think it's giving sub-second accuracy, but it updates rapidly with changes in the current draw and gives you a pretty good idea what is going on.  That said, since it doesn't report a peak wattage it's certainly more effective at measuring steady state situations - idle, parity check, etc.

I loved my Kill-A-Watt until it died testing a fridge overnight.  The fridge failed too and probably overloaded the device.

 

For a PSU I would say 20W per drive (assuming all drives start at the same time and not staggered).  The rest of the system shouldn't exceed 100W unless you're using old hardware like me.  Most PSUs are most efficient at 50% load.  If I have a 10 drive system that idles at 50W then I would want a (20*10+50)/.5 = 500W PSU to feel comfortable.

What is the most accurate tool or mathematical equation to calculate a power supply for unRAID?

 

I'm looking for something that's dynamic.

 

Thank you

anvien

 

Do you want to calculate the power supply requirement? or are you trying to measure the power usage?

 

The calculation is almost always for the startup demand, which the tools listed do not show.

 

Something like my Extech MA200 Meter with Max hold (which none of the P3 KillaWatt do) will catch the startup load. But even MA200 misses the inrush demand, the MA1500 does that.

 

That website will sell you a nice huge power supply.

Just out of curiosity, since the OP is "new" in here - do you know the PSU thread?

 

There are some information about dimensioning and examples you can lean on.