Question about Power Supply

[sakh1979]

I have a 400W power supply in my unRAID box, how many drives can it safely support?

 

Thanks,

Sagun

[Thornwood]

Maters on the kind of drives.... and there power needs.

[Rajahal]

More important than the wattage is the amps on the +12V rail(s), as that is what will be powering your hard drives.  Please post your power supply's model number so that we can check the amps for you.  You may also be able to read the amps off the sticker on the side of the power supply.  It should say something like 12V(1) - 14A, 12V(2) - 15A.

[sakh1979]

Thank you all for the reply! Raj here is a link to NEWEGG describing my power supply:

 

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139008

 

Thanks,

Sagun

[daniel.boone]

Thats a 30 amp single rail on the 12 volt line.

 

5400 rpm drives use about 2amp, 7200 use about 3amp

 

I ran 12 drives with a 550w corsair. When I added the 13 the array would not spin  up all the drives. I would remove one and all was well again so i bought a 750w

[sakh1979]

Thanks Daniel -

 

So, my 400W power supply will 10 5400rpm hard drives easy?

 

Sagun

[Rajahal]

As Mr. Boone said, you have 30A to play with.  Estimate 2A for each green drive and 3A for each 7200 RPM drive.  Leave about 2-3A of headroom to power the motherboard and fans.

 

Your PSU will power up to 13 green drives, 9 x 7200 RPM drives, or a mixture thereof.

[daniel.boone]

Thanks Daniel -

 

So, my 400W power supply will 10 5400rpm hard drives easy?

 

Sagun

 

Yeah that's the general idea. You can always add something that draws more power than planned. There is something to be said about efficiency as well. Adding too many 7200s and the total possible drops faster than you think. I kinda wished I bought a 850. Gettin tired of having to replace stuff. These arrays grow quickly.

[Joe L.]

I kinda wished I bought a 850. Gettin tired of having to replace stuff. These arrays grow quickly.

and... the drives are getting bigger....

AND some manufacturers are standardizing on 7200 RPM drives to eliminate inventory duplication.    Current demands will keep increasing as your array grows.  The power supply is one place NOT to skimp on quality.

[dikkiedirk]

I kinda wished I bought a 850. Gettin tired of having to replace stuff. These arrays grow quickly.

and... the drives are getting bigger....

AND some manufacturers are standardizing on 7200 RPM drives to eliminate inventory duplication.    Current demands will keep increasing as your array grows.  The power supply is one place NOT to skimp on quality.

 

Very true indeed. An electronic appliance is as good as its power supply. Crappy power supply means crappy server.

[WeeboTech]

What I'm reading in specs is that 7200 3TB drives pull 2.0A max,peak and 5400's are between 1.75 & 2.0A Max,Peak.

 

30A on the 12V rail will safely power 10 drives up to 7200RPM.

 

What's required is leaving headroom for the motherboard, ram, fans, etc, etc.

 

What kind of CPU and Video card can have a big effect on this though.

[dgaschk]

Thanks Daniel -

 

So, my 400W power supply will 10 5400rpm hard drives easy?

 

Sagun

 

The wattage is not important. Think of it as a "30 Amp" power supply.

[sakh1979]

Thank you all for all the valuable inputs, I learned something here.