PSU Recommendation for Server

Methanoid

Methanoid

Methanoid

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Joined
18 Oct 2002
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I run FlexRAID which requires a lot of drives but one parity drive.

My specs will be:

i5-3570K @ 4ghz on default volts
2 x DDR3 8Gb
Intel IGP
120Gb Sandisk SSD
18 x 3Tb WD30EZRS drives (WD Greens)
DVD-RW drive
2 x LSI SAS Controllers (PCIEx8)
1 x 120mm fan (CPU)
4 x 140mm fans (airflow)

The PSU calc here recommends
Minimum PSU Wattage: 389 W
Recommended : 439 W

I have a Silverstone Strider Gold SST-ST55F-G 550W PSU which current powers 11 HDDs in similar spec system.

Storage Review says that the HDDs require 2W at 5V and 10W at 12V so that is a current draw per HDD of 0.4A @ 5V and 0.83A @ 12V. All the HDDs would total 7.2A @ 5V and 15A @ 12V. That is well within specs.
** No hotlinking **
http://www.storagereview.com/images/low_power_power_values(4).png

The next issue might be cabling. 18AWG cable can take 6-7A

That means 5 HDDs per cable. The Silverstone only has 3 outputs that are live (4th is capped off on the 550w model)

CA-313-SV_74870_350.jpg


That means it probably cannot run more than 15 HDDs.

So, PSU recommendations? I think I need FOUR modular outputs for the HDDs/DVD/SSD (5 SATA on each, will make up cables). I think around 500W but will take opinions. I guess if I went to 650W I could chuck in my GTX970 (TDP 145W and nearly all 12V). Needs to be GOLD and semi modular. I prefer the shorter PSUs as the longer ones make it harder to fit cabling.
 
I read your post a week ago and it got me thinking and so I did my own investigation. There are quite a few sites I've found that, depending on the length, suggest you can get a great many more amps than 6 down 18AWG in short runs.

http://www.powerstream.com/Wire_Size.htm indicates up to 16A.
http://www.engineeringtoolbox.com/wire-gauges-d_419.html indicates between 9.5 and 5.6.
http://electronics.stackexchange.com/questions/38515/what-is-the-max-current-for-awg16 would suggest that it's dependant on how warm the cable can get. Given that it's going to have some airflow over it, you can probably tolerate a higher current.

I think in my fileserver I have 6 7200 RPM drives running off the same molex/SATA PSU cable. It's never shown itself to be an issue.

You could do a dry test of the PSU with just the HDDs to see if you can get all of them split across the 3 outputs.
 
reading your power consumption link it seems spinup time is 17s @ 10w per drive i can't imagine the small bit of extra load for 17s would ever pose a problem.

which means if all 15 drives were seeking at the same time [unlikely but very possible] it would be around 7.8 amps
 
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