How big a PSU for this unRIAD rig???

[Redstorm]

Hey Guys

 

Just wanting a little validation on my plans / calculations

 

I am already running unRAID on a little HP microserver but that was always an interim solution. As it fills up, I need to start firming up my long term plans and buying / blagging components.

 

I want to build a 16/17 drive server in a Fractal Design DEFINE XL case (10x3.5" drives as std then a 5in3 cage using up 3 of the 4 5.25" drive bays and finally an x-swing in the top bay to give me 17 drives. 15 drives will be data drives with one parity and one cache drive (may opt for SSD on the cache drive - 128GB should be fine, no?)

 

I have read the forum and see that you recommend allowing 2A per green drive and 3A for 7200rpm drives. so I was thinking 17 * 2A = 34A*12v = 408W + 60W for the mobo takes it to 468W for an "all green" server. But 17 * 3A = 51A*12v = 612W + 60W for the Mobo = 672W for a "not so green" server. On the basis that I will probably use green drives for both energy efficiency and noise reasons then I was thinking that a 550W PSU ought to be sufficient allowing for a bit of overhead. Since I am using my unRAID server to store media files, I can't imagine a situation where all drives would be spun up at the same time, save for perhaps doing a parity check or on boot.

 

So I am just wanting to know if you think 550W would be enough for my build or would it make sense to go for 650W and be safe?

 

I hear Corsair are pretty good quality and fairly reasonably priced. Any other recommendations for a decent / cheap PSU at this power point would of course be greatfully received.

 

Many thanks

 

[c3]

The Corsair 550W http://www.newegg.com/Product/Product.aspx?Item=N82E16817139032 has 45A on the single 12V rail. Which is more than the 600W, so check the details for the model you are shopping.

 

I look for Plus 80 Gold to reduce the amount of heat being dumped in my house. So the SeaSonic 560W 46A http://www.newegg.com/Product/Product.aspx?Item=N82E16817151098 would be my pick, but more money. But often on sale.

 

You do want to size the power supply as close as possible. The efficiency falls off at low utilization (and over utilization). Since these servers can idle down very low ~20-60W, they end up outside the high efficiency range (20-80% utilization). 20% of a 550W is 110W, you'll have no problem getting under that. The only time you'll see the 40A is an non staggered powerup.

[Redstorm]

Thanks for the prompt reply.

 

I read that Seasonic are the "Rolls Royce" of power supplies but fear my budget won't stretch to that.

 

Besides, I live in the UK and everything tech is more expensive here. Its often a case of just swapping the dollar sign for a pound sign and the numbers stay the same meaning we pay around 50% more for most kit compare to those who are stateside.

 

Also living in the UK, excess heat is less of a concern (probably a bonus for most of the year  )

 

So do you think then that going for something like Corsairs CX430 would be ok then? Or is that risking too much if the server spins up all the drives at the same time?

 

Thanks

[dgaschk]

UnRAID requires concurrent access to all drives during parity build, parity check, failed drive emulation, and drive rebuild. These are not the times when you want to discover that your PSU can't cut it.

[c3]

UnRAID requires concurrent access to all drives during parity build, parity check, failed drive emulation, and drive rebuild. These are not the times when you want to discover that your PSU can't cut it.

 

Yeah, you shouldn't go below the 40A if you are going to have 17 green drives. The 28A of the 430W might bring surprise later.