Low power NAS build - Pico PSU or "regular" PSU?

[Lonyo]

I'm hoping to build a NAS box for up to 6 drives based around an Atom motherboard.
(http://pden.zotac.com/index.php?pag...&category_id=7&option=com_virtuemart&Itemid=1)

I'm not anticipating a huge amount of power draw from the HDDs (since they will be low power drives, typically 7w or less under read+write) so from the HDDs + a single stick of RAM + Mobo/CPU I would expect a sub 60w power draw. Nothing else would be attached (save for many some 3.5" externals via USB/e-SATA which would have their own power).

My two options (in the UK) seem to be:
1) http://linitx.com/product/13062
150w FSP 1U power supply. Only three outputs (4-pin + 2xSATA) so I would need some adapters to go with it to hook up all the drives.
Efficiency seems ot be 70% and output is 120w from 12v (10A).
http://www.fsp-group.com.tw/english/1_product/2_detail.asp?mainid=1&fid=152&proid=605

2) http://linitx.com/product/12383
Pico PSU, 150w, presumably only supplying 12v. I have no experience in Pico PSUs, so I don't know whether only 12v is fine for a PC (I assume it is otherwise they wouldn't sell them...).
Since it only has one of each output (4pin/SATA) I would need a lot more adapters to daisy chain drives. The efficiency is much higher (96%), but so is cost (3~4x the price accounting for everything).

Noise isn't an issue, since it will be located far away from anywhere people would be.
Am I missing an option or is it pretty much only these two things which are available/make sense? I want as much efficiency as possible, but I also want to be as inexpensive as I can get away with for a decent final product.
There don't seem to be many sub-200w PSU options available generally that I have seen, and the lower wattage FSP readily available is a fanless 120w which costs 2x as much as the 150.

Could I go even lower on power than 150w if I could find something reasonably priced? I am only anticipating 60w peak use, so even 90w should be more than enough, right?

Thanks for any input.

 

[dowxp]

I would say 150W sounds about right --

 

[fffblackmage]

Despite the fact that HDDs don't use all that much power when they're already on, they need more in order to start spinning the disks during boot. I don't know if this will present a problem or not, but my assumption would be probably not, unless you add more HDDs.

If I'm not mistaken, the Pico PSU takes in around 12Vdc and converts that to the 12Vdc, 5Vdc and 3.3Vdc a computer needs. What this means is that you need to also get a ~12V wall adapter in addition to the Pico PSU. Even though the Pico PSU has high efficiency, you'll also need to factor in the wall adapter's efficiency. The point of the Pico PSU is really for an application with tight space constraints, so you might be better off with the conventional PSU.

 

[fuzzymath10]

Despite the fact that HDDs don't use all that much power when they're already on, they need more in order to start spinning the disks during boot. I don't know if this will present a problem or not, but my assumption would be probably not, unless you add more HDDs.

I think many PSUs power up hard drives staggered (one at a time rather than all at once) to prevent a strain on the 12v rail. This only works with native SATA power plugs (not molex to SATA IIRC) and I can't remember how it's configured.

 

[mindless1]

HDDs are only spun up staggered with add-on RAID controllers designed to do so, or if the motherboard bios (and chipset of course) specifically has a setting you can toggle on (but it would be off by default).

Yes the linked Pico PSU takes 12V DC input (like from a car or off-grid battery power), it isn't really suitable since you'd have to buy the 12V AC-DC PSU too.

Factor 2A /12V rail spinup current per drive if you can't find any evidence that this specific motherboard supports staggered spinup, UNLESS you already have the drives and they list a max current which you can add up yourself. However, you might be able to get the linked FSP to work anyway, IF it has enough feedback on the 12V rail to keep that rail's voltage high enough with such a large difference in 5V rail current at startup.

I second the suggestion to use a conventional (mATX) PSU.