BUILD First FreeNAS Build, is the hardware I've chosen enough for my goals?

[Nick2253]

I tend to trust more a datasheet than a flyer. You can't say that "max" is the proper label just because you want it to be that way. Anyway even if it's the max value you always want to use the worst case scenario when you design a system for reliability so in the end we don't care.

I don't say that it's max "just because I want it to be that way." I say it's max because "max" is consistent with other manufacturers' data sheets, it's consistent with the flyer datasheet, and it's consistent with real-world tests of power draw. The evidence that 2A is a "max" draw and not a typical draw is amazingly conclusive. In fact, the only place where it's not called out as max is in that Seagate product manual.

Just to sanity check it, you're trying to tell me that a 5900RPM NAS drive has exactly the same "typical" startup current draw as a 7200RPM drive? Compare the Barracuda manual to the NAS manual: the Barracuda has increased power use (more than twice as much) in every way, other than startup. Again, for both these drives, the startup current is called out as "max" on the flyer.

You also continue to fall back on "always use the worst case". Like I've already said, even in the worst case, 300W is more than enough. 24W*6 drives + 54W CPU + 3W*4 DIMMs + 24W fan + 50W motherboard/other components (and that's pretty ridiculous power consumption) is 284W. Which is the worst case peak usage. Which is still less than 300W. Typical peak usage will be significantly less, especially with a few minor design decisions. And, let's be real, your motherboard and other cards are not drawing 50W, even at peak.

With staggered spinup, you get your theoretical peak usage down under 200W. Even with simultaneous spin-up, your in-practice peak load is going to be under 200W (we know empirically that HDDs don't need 24W to spinup, and CPUs don't draw their full TDP during bootup). Pick some fans that don't pull 2A (not that hard to find), and do a better job of accounting for your motherboard power draw, and you're now in the sub 240W territory in the worst case, which is below our 80% threshold.

and I wanted to know where you've taken the measure. As I suspected you measured on the AC side but the PSU has pretty big capacitors inside and they smooth the power peaks you can have on the DC side (let alone the averaging of the meter you've used if it's a killawatt meter or similar, they're also not TRMS, only RMS) so the power peak is in fact much larger than what you read on the meter.

My meter is slightly better than a killawatt. I've got a TRMS clamp meter from our facilities department. It's an Extech something or other; I forget the exact model number. Also, "much larger" is a bit of a stretch. Like I said above, peak usage, in the worst case scenario, should still be under 200W thanks to staggered spinup.

It's not a fan in particular, it's the specs you use when you design a fan (like you use the ATX specs when you design a PSU for example). I searched it (I downloaded it a while ago as it's hard to find) and found it here: http://www.formfactors.org/developer\specs\4_Wire_PWM_Spec.pdf (page 9)

Again, that's the worst case scenario allowable on the wire, not necessarily the spec for the particular fan you install. For example, the Noctua NH-F12 fan spec says its max input current is 0.05A. That's less than a watt. Just because the PWM spec allows a fan to draw that much power, doesn't mean you have to pick a fan that draws that much power. But again, even if we allow a fan to draw 2.2A, we are still within spec of our 300W PSU.

 

[Bidule0hm]

I'll not continue to argue but I'm still curious to know how many people here use staggered spinup? do you?

 

[cyberjock]

I not only don't use it I don't even recommend it.

The problem is that staggered spinup is something that requires the SATA/SAS controller to support it properly (and they don't always support it properly) as well as the hard drive. You'd be amazed how many drives and controllers I've seen over the years that work, except if your harddrive has a certain revision of firmware, or you update the controller, etc. It's something that seems to be pretty fragile when buying a bunch of hardware and effectively "hoping" it will work. And if it stops working because you did something... let's say you upgraded from P16 to P20 firmware... how long will it take for you to figure it out, and will you find out "after its too late"?