Proposed build config - comments requested

[Kevin Horton]

I'm putting the parts list together for my first FreeNAS box, and would appreciate any comments. It will be the first PC I've ever built, so don't make any assumptions about my knowledge. I've read the the Hardware Recommendations in the FreeNAS docs, the various stickies in this forum and any threads that my searches found.

NAS Purpose - media storage, business document archiving, and Time Machine backup from several Macs.

The system will be configured in RAIDz2.

Case: Fractal-Design Node 804 (already purchased)

CPU: Pentium G3458 (possible future upgrade to Xeon if some future use case demands it)

Motherboard: SuperMicro X10SL7-F

RAM: Crucial CT102472BD160B (2 x 8 GB sticks)

Hard Drives: 6 x 4TB Western Digital Red (the case can support up to 10 drives, and I won't rule out going whole hog in the future)

Power Supply: Seasonic SS-500L1U, 500W, Gold certified. It can supply up to 480W on the 12V lines, so I should be good with the 12V current, as long as the total load is OK. The info I can find that actually has actual 4 TB NAS drive startup current suggest that the current per drive should be somewhere between 3A and 3.5A at 12V, or 35-40W per drive, and that peak should last 3-5s (or maybe it is half that value, as the data from another poster at the end of the thread is exactly half as much). The WD spec sheet claims a peak drive current of 1.75A at 12V, for whatever that is worth.

I hope to use this NAS for three to five years, with upgrades along the way as necessary. I want to spec the NAS to leave the option to upgrade the hardware in the future if I decide to also use it as a Plex server - hence the choice of a motherboard that can support more powerful CPUs, even though my current needs could probably be met with an Avoton C2550 or C2750 on an ASRock board.

Questions:

1. is a 500W power supply enough handle possible expansion to 8 or 10 drives in the future? If I went with a larger capacity power supply now, with 6 drives, it would be running at a very low percentage of its rating, when at idle.
2. Is it possible to configure the described system to do staggered drive startup? If so, I could probably get by with a smaller PSU, and try to run it more in its efficiency sweet spot during normal operations.

 

[Marc Leonard]

1. My guess is 500w should be fine for that amount of drives.
2. Just, don't. Don't try and cheat it. Get 500w and you know it will be ok.

 

[tvsjr]

Rather than guess, why not use jgreco's power supply sizing guide here: https://forums.freenas.org/index.php?threads/proper-power-supply-sizing-guidance.38811/unread
He uses math and science and stuff, which seems to work better than guessing.

 

[Marc Leonard]

Right. And use that ^
Forget to mention that.

 

[Robert Trevellyan]

I've read the the Hardware Recommendations in the FreeNAS docs, the various stickies in this forum and any threads that my searches found.

:D

Looks like you're on track.

 

[Kevin Horton]

I had read the power supply sizing guide before posting this thread. The math in there is pretty straightforward, if you can get good power data for the various components you are using. I'm not convinced that it is reasonable to assume the CPU is running at its design TDP when the hard drives are starting up - it shouldn't be working too hard when the NAS starts up, so I'm assuming 50% of the TDP.

Using the data from manufacturer's specs (where I can find them) and best guesses in other areas, I come up with a max load during start up of 310W, which suggests a 400W power supply would do. I'd like an extra conservative factor to account for the fact that some of the best guesses might be wrong, so I'll go with 500 W. I don't want to go too high, as the efficiency falls off a cliff at low power, and this thing will be idling most of the time. I also wonder how good it is for PSU longevity to run it so far off its design point (i.e. run it at very low power)

 

[tvsjr]

Everything runs roughly "wide open" until the BIOS POST occurs. My Supermicro chassis (which is a 4U beast) runs in the 550-600W range when booted and cruising along... I've seen it hit 1.2KW at boot thanks to the drives spinning up, fans at maximum, processors run up, etc.