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post #21 of 33
In this case you do want overkill wattage, due to something called "transient response".

When a large load is placed on a power supply it takes a few milliseconds for it to adjust. During that time voltage will drop precipitously, then gradually rise back to where it needs to be.



HardOCP does transient response test, loading a 10A or 20A load onto the +12V output of a PSU, with a ramp up time in the microseconds. Many smaller PSUs fail the test; even high-end PSUs suffer large voltage drops. With your 18 hard drives you'll be dropping 35-45A, plus the other components in your system, onto the +12V rail all at once when you start up. A multi-rail PSU's OCP may trip, short circuit protection may trip, and you will definitely see a huge voltage drop lasting for several milliseconds, unless you choose very carefully.

Surprisingly, many 80PLUS Gold power supplies do very poorly in transient response tests, due to the LLC-resonant half-bridge or full-bridge topologies used. Forward topologies, like double forward and active clamp forward, suffer much less voltage drop in transient tests, if properly designed and with adequate secondary capacitance.

SeaSonic X is an LLC-resonant half-bridge unit. It does very poorly even with just a 20A transient load. With nearly 50A it could easily go out of spec instantly upon start and could just shut down.

FSP Aurum is an active clamp reset forward topology, and does a bit better in terms of transient response. It may be the better choice.



I recommend doing something I normally recommend against. Take an FSP Aurum 600W and put your main system and six HDDs on it. Then take a 500-600W 80PLUS or 80PLUS Bronze PSU and use that to run the other 12 HDDs. Most PSUs in that class use a double forward topology that handles transient loads relatively well, and since the HDDs won't consume all that much power after spinup, the additional electricity cost from the lower efficiency PSU will be minor.
post #22 of 33
Thread Starter 
Quote:
Originally Posted by Phaedrus2129 View Post
I recommend doing something I normally recommend against. Take an FSP Aurum 600W and put your main system and six HDDs on it. Then take a 500-600W 80PLUS or 80PLUS Bronze PSU and use that to run the other 12 HDDs. Most PSUs in that class use a double forward topology that handles transient loads relatively well, and since the HDDs won't consume all that much power after spinup, the additional electricity cost from the lower efficiency PSU will be minor.
Would an Aurum even be worth it in that case? Or should I just get two M12II's? I'd like to keep this under $180, any suggestions?
Edited by zouk52 - 6/18/11 at 5:10pm
     
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post #23 of 33
Well, the Aurum is very efficient, and running the bulk of the system on it would net some decent gains in that way. But just stay away from LLC resonant half/full bridge designs, and for 80PLUS Gold units in that budget that just leaves FSP Aurum.
post #24 of 33
Thread Starter 
Quote:
Originally Posted by Phaedrus2129 View Post
Well, the Aurum is very efficient, and running the bulk of the system on it would net some decent gains in that way. But just stay away from LLC resonant half/full bridge designs, and for 80PLUS Gold units in that budget that just leaves FSP Aurum.
Alright then, I'll grab the Aurum and an S12II 520. Is there a guide somewhere on how to connect them to power on together?
Edited by zouk52 - 6/18/11 at 5:10pm
     
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post #25 of 33
Rather than an S12II, you could get an Antec NeoECO 520C, which is basically just an older version, and is much cheaper.
post #26 of 33
Thread Starter 
Quote:
Originally Posted by Phaedrus2129 View Post
Rather than an S12II, you could get an Antec NeoECO 520C, which is basically just an older version, and is much cheaper.
Wow, it's way cheaper! I'll get that instead. So I guess the S12II is the same thing with tweaked efficiency?
     
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post #27 of 33
Quote:
Originally Posted by zouk52 View Post
Wow, it's way cheaper! I'll get that instead. So I guess the S12II is the same thing with tweaked efficiency?
Pretty much. Maybe slightly better electrical performance, some different component choices, but it's the same platform.
post #28 of 33
I think it's simpler and no problem if you just get a single Seasonic S12D (should be double forward--anyway, transient response and low level efficiency are pretty good) or maybe FSP Aurum 700W. You'll get better efficiency with a single PSU.
post #29 of 33
Thread Starter 
Quote:
Originally Posted by Phaedrus2129 View Post
Pretty much. Maybe slightly better electrical performance, some different component choices, but it's the same platform.
Actually, might there be a single PSU alternative I could use? I'd have to mod the case to fit 2...
     
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post #30 of 33
If you're willing to sacrifice efficiency, there are lots of 850W double forward units that could work it, but I was trying to still get you 80PLUS Gold for most of the system.

Actually, I just remembered that the Strider Gold units are double forward.
http://www.newegg.com/Product/Produc...one-_-17256067

But they're out of your budget.

This would work though:
http://www.newegg.com/Product/Produc...-058-_-Product


I completely forgot about the Strider Gold line, and forgot that the Strider Plus units were so cheap.
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