I am not sure what PSU I could get away with for a 12 HDD unraid system.

I have used a 650W in the past but can I get away with a 600W or even a 500W PSU

 

Most drives will likely be 7200RPM drives

 

Thanks

...it'll depend on the other components, but I'd get a 12V-30A+ single rail PSU (for 12 HDDs you need 24A+ for these alone).

 

The Corsair VS450  and the CoolerMaster G450M are both spec'ed at 34A and the seasonic G-360 is rated with 30A, as an example

Looking at an Intel G2030 CPU, 4GB RAM

There will eventually be 12 7200RPM HDDs

Maybe 2-3 fans

 

I know a 650W PSU is enough because that is what I have in my other 3 towers but I am wondering if I can go with a 500W and it would be ok

 

 

....IMHO the 450W PSUs with 34A are plenty....assuming that the 7.2k drives

are of "newer make&model"..these have the same cold-start consumption as the older "greens",

which is 2A, and not 3A each as stated in the PSU thread.

My NAS with 20+ drives, (11x green 2TB, 9x 7.2k seagate 3TB, 3x older enterprise 1TB samsung F4) is measured with peak 420Watts during cold boot.

And this is an 1156 with XEON L3426, 32GB and 6x noisy fans, each drawing 0.25A.

Agree -- 450w with a single 12v rail is plenty as long as you use a quality unit.

 

OK I am going to get this one:

 

http://www.directcanada.com/products/?sku=11180AC1629

 

That will probably work; but the CX series is Corsair's lowest-quality line -- I've seen systems that won't work with those that work fine with the TX, HX, AX, RM series power supplies.  I'd step up to a better quality unit.  Looking at the same supplier's options, I'd go with this:  http://www.directcanada.com/products/?sku=22170AC3230&vpn=ST50F-P&manufacture=Silverstone Technology

 

I'm sold on 80+ Gold or better for buying new PSUs.  The increased efficiency doesn't generally cost that much more and depending on your usage scenario may pay for itself in a couple years.

 

You can find the results of the 80+ cert online at http://www.plugloadsolutions.com/80pluspowersupplies.aspx

 

If you're going to be operating your server 24/7 over several years then it is worth your time to do some simple calculations to estimate how much you'll spend in that time on electricity.  The break point for me on a five-year calculation was with a power scenario of 65 watts.  With my cost per kilowatt-hour the more efficient gold units paid for themselves compared to the much cheaper bronze units.

 

Calculate as follows:

1) Choose an average power scenario based on your system and likely usage.  I'll use 100 watts for this example.

2) Look up the efficiencies for the given PSU at the above-linked web site

3) Calculate the average load by dividing scenario by PSU capacity.  For a 500 W power supply that would be 100 / 500 = 20%

4) Interpolate as needed to get an estimated efficiency at the given load.  For illustration let's say my PSU is 85% efficient.

5) Divide server power by the efficiency to get a measure of how much AC will be drawn from the mains: 100 watts / 85% = 117.6 watts

6) Multiply by the number of hours in a year, then divide by 1000 to get the kilowatt-hours in a year.  117.6 * 8760 / 1000 = 1030 kilowatt-hours

7) Multiply by the cost per kilowatt-hour to get your annual cost for electricity.  Mine is about 15 cents per kilowatt-hour.  1030 * $0.15 = $154.50

 

Now if I have a unit that is 90% efficient at the same 100 W power draw, then the difference is:

100 watts / 90% * 8760 / 1000 * 0.15 = $146.00 per year.  Over five years the savings is $42.50 which easily justifies for me the increased cost of a Gold PSU.