Active vs Passive Heatsinks (in Supermicro Chassis)

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NablaSquaredG

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Aug 17, 2020
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I'm wondering:

What are your preferences regarding active vs passive coolers in servers when performance is key?

All Supermicro 2U servers I know are originally shipped with passive coolers, yet they have active coolers in their portfolio.

Also: Would you prefer Dynatron or Supermicro coolers?
 

BlueFox

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Oct 26, 2015
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Supermicro offers active coolers for systems that don't have forced airflow (eg desktop towers). The majority of rackmount servers are intended to be used with passive heatsinks. Putting in an active heatsink in a system with forced airflow would be detrimental (or passive in one that doesn't), so you'll just want to use the correct one for the chassis.
 

BlueFox

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An active heatsink is going to be designed to cool just the CPU and not other components, which means it can reduce airflow and static pressure. Having a second slower fan does not multiply airflow, but generally the opposite. With a passive heatsink, you obviously also get a much larger one than you would an active one for any given size.

As for brands, either is fine. There's not a whole lot to heatsinks and given the size constraints of rackmount form factor, I doubt you would notice a difference between the two.
 

Fallen Kell

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Mar 10, 2020
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Putting in an active heatsink in a system with forced airflow would be detrimental (or passive in one that doesn't), so you'll just want to use the correct one for the chassis.
Well, there is most certainly a use case in which you swap out the super high noise fans for much slower moving and quiet ones. At which point, you then need to install heatsinks with active cooling to make up for the loss of airflow in the chassis. Overall, you can make the system a lot quieter, and still have proper cooling.

This works best on 3 and 4u systems where you can usually replace the high speed 40mm fan walls with 120mm or 140mm fans with some ingenuity.
 

BlueFox

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3U and 4U systems seldom use 40mm fans. CFM is not the only factor. Static pressure is also quite important, which will not be anywhere as high with slower fans.
 

ca3y6

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Apr 3, 2021
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Active heatsink + Air shroud for best cooling and noise results
Actually I wondered about that when I built my server. I am a bit of an amateur, and my thinking was that the air shroud was robbing the PCIe cards of their airflow, and high end SSDs tend to heat up too. So I went for no air shroud plus an active cooling for the CPU (1 socket). Both CPU and SSDs seem to be cool so I think I am OK but I wondered if I didn't make the matter worse. Would you use a passive heatsink without an air shroud in a 2U server?
 
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i386

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Mar 18, 2016
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Would you use a passive heatsink without an air shroud in a 2U server?
No.
I am a bit of an amateur, and my thinking was that the air shroud was robbing the PCIe cards of their airflow, and high end SSDs tend to heat up too.
The air shroud helps to guide the airflow through cpu heatsinks and over ram and other parts near the cpu. For better cooling of addon cards the server chassis/mainboard is usually divided in two zones. On supermicro gear the first zone has numbers and is controlled by cpu temperatures (fan_1, fan_2 etc.) and usually has an airshroud, the second zone has letters and is used for cooling "system components" and add on cards (fan_a, fan_b etc).
Under Ipmi there is a setting called "heavy io" which runs the fans at higher rpms in the second zone.
Screen Shot 2021-08-31 at 12.57.35.png
I think other vendors have similar approaches for cooling cpus and add on cards.
 
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Fritz

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Apr 6, 2015
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Dynatron coolers are garbage. They don't cool anywhere near as well as SM coolers. At least that's been my experience.