I had outfitted my new FreeNAS box with Noctua fans, but my HDD were still getting a bit hot during scrubs. Both fan placement and fan performance are crucial, and I had to go back down the rabbit hole to find a solution.
A Good, Quiet(ish) Fan
A good review site is a great start.
You might need a cubic meter per hour to cubic foot per minute calculator because everyone seems to love using alternating units. Here’s one.
tl;dr – If your focus is keeping the noise down and you won’t be using PWM, go for the Phanteks PH-F140HP PWM. If you’re using PWM, go with the Bitfenix Spectre Pro PWM as it is similarly quiet when spinning slowly, and pushes far more air when spun up to speed. For a lark, I’ve included the fan I have in all my cases. Not very “stealthy” when you’re nearly as loud as a leaf-blower and push only 40% of the air. Has fan technology really come that far, or was I just a terrible consumer back when I bought them?
Vantec Stealth SF12025L 53 CFM @ 28dB
Noctua FLX 67 CFM @ 19dB
Noctua PWM 82 CFM @ 26dB
Phanteks PH-F140HP 88.6 CFM @ 19dB
Phanteks PH-F140SP 82.1 CFM @ 19dB
Bitfenix Spectre Pro PWM 122 CFM @ 29dB
One thing to note is that the Phanteks PH-F140HP is a 140mm fan but it’s mounting points reside at 120mm. If your case can’t accommodate that, opt for the Phanteks PH-F140SP.
I ended up getting two Bitfenix Spectre Pro PWMs because I could source them locally. The build quality on both of them was garbage, but they’re cheap and whisper quiet when running off PWM power. They only get loud when your computer decides temperatures have risen to unacceptable levels, or your SuperMicro motherboard thinks the fans have died. A fantastic solution to that is posted here.
Placement
For placement, bit-tech did a great test running 0-7 fans in a myriad of configurations. The whole article is worth a read.
1. The amount of venting in your case can have a huge impact on cooling, particularly around the CPU area. If you have fan mounts here that are blocked up, unblock them. 2. Generally, all other things being equal, it’s better to get hot air out of your case than to pump cool air in, particularly when it comes to CPU cooling. 3. If you have a roof mount that’s located nearer the front of the case than the CPU cooler, leave it open. Fitting a fan here only causes problems. 4. If you have one, two or three fans in your case, the side panel intake mount is the most important. Fill this first, followed by the rear exhaust mount, followed by the roof exhaust mount. 5. Bear in mind the fact that fans have an effect on each other and use this to your advantage. For this to work though they need to be close enough to interact - a side intake works better with a rear exhaust than a front intake does for this reason. 6. With four or more fans, concentrate on traditional front to back cooling and creating one strong, continuous air flow. Fill the front intakes and the roof and rear exhausts first. 7. More fans does mean more cooling, but expect diminishing returns when going above three or four fans.