NAS/fileserver project—RP64 in 1U ATX/ITX case (comments welcome!)

[TRS-80]

It have been some years since I was looking for a power supply in this range, but last I was (maybe 4-5 years ago, I guess when I was setting up my Cubietruck probably) the smallest ATX supplies available at that time were still hundreds of watts (with the exception of that little pico one).  And when you are that far outside of the intended specs of a power supply, you are going to be using it extremely inefficiently.  I know it's not a big deal in the grand scheme of things, but still.

Also then you have the issue of ATX signalling to turn the power on and off and on which is probably not rocket science but still, just more research and complexity.

For all those reasons, I personally feel that ATX power supply are totally inappropriate for this use case.  But, as you seem bound and determined, go ahead and knock yourself out.  lol  I dunno, maybe you have one "laying around" or whatever that you want to use.  We probably all do.  I personally would still not do that, unless I was extremely strapped for funds.

I would power the drives directly from there and not through the JST connector on the board since I doubt the board and the connector were designed/tested with such electrical loads in mind.

I agree with you here, which was exactly why I had planned to bypass it entirely and just run the drives directly off the main power supply.

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EDIT:  There seems to me like a lot of speculation (and a number of variables like startup, etc.) around about proper sizing of power supplies.  Maybe when I get this all working, I post a video or some other data to help others who are DIY their own NAS in the future.

Some more data points in the meantime.  I thought for sure I had posted a link to this already, but there is a post at Armbian about ROCKPro64 as NAS? where I was getting at least some of my estimates from.  FWIW, I plan on eventually adding 2 more 3.5 HDD, for a total of 4.  Estimate in that thread for this use-case was 12V@8A (by soerenderfor).

This is also very close to Helios64 (which actually have 5 (full size) drive bays, but also charge a battery and some other additional things).  But we can use that as yet another data point.  And their power supply is 12V 10A (efficiency : 85%).  In fact I found that info just now on Helios64 Power Consumption section of Kobol Wiki, where they actually list a fair amount of data which I suspect you guys might find interesting.