92mm fans for Noctua NH-U9DX i4 that aren't so slow?

5mall5nail5

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Nov 16, 2015
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Hey guys - I have a Supermicro SC846 chassis running dual E5-2670s, 256GB of RAM, 16 x 8TB disks, and 8 x Intel S3710 400GB SSDs. It's an ESXi box for my lab. I am using Noctua NH-U9DX i4 on each CPU. I was up around 75 - 80% RAM utilization and started getting a "high non-critical" (80C) alarm on a DIMM or two. I had swapped in some desktop, lower speed fans into the chassis fan holders because the server was in a spare bedroom and I didn't want to hear the noise so bad.

Now the server is in the basement which is a constant 72 - 74F and so I put the original fans back in. The noise is not very noticeable with the standard or optimal fan profile. However, I've got a couple hardware status alarms so far for CPU fans because the Noctua NH-U9DX i4 fans are so slow - 600RPM, which triggers an IPMI alarm. I could modify the alarm to be around 500RPM (should never really hit that) but the reality is, I wouldn't mind some faster CPU fans since the unit is now in the basement.

Can anyone recommend a 92mm fan that would still be PWM but spin faster at lower PWM%?

Thanks!
 

EffrafaxOfWug

Radioactive Member
Feb 12, 2015
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There's been a few people, myself included, who've had issues with Noctua fans running at perplexingly low rpms under supermicro IPMI - some chassis fans of mine would frequently report 0rpm and thus trigger an assert which would breifly spin all the fans up to max. Annoying.

If your current setup means noise is no longer an issue and the chassis fans are doing their job, you can really just chuck in any cheap fan that runs fast enough, although ideally you'd want ones with decent static pressure. But I suspect any 92mm you have lying around will fit and work OK.
 

StevenDTX

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Aug 17, 2016
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Just change the fan thresholds with ipmitool if the cpus are staying cool enough.
 

5mall5nail5

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Nov 16, 2015
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Thanks guys - here's what the fans are currently doing (this is "optimal mode" at the current time)


Here are the temperatures in the system (not showing all, obviously) sorted from highest to lowest:


The ESXi host has the current loads (kcloud1esx1 is the supermicro, the second is an R620):


So I am tempted to just move the thresholds... The fans running 900 and 825 RPM are the CPU coolers (4 92mms, 2 on each HSF in a front/back combo)
 

i386

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Mar 18, 2016
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I could modify the alarm to be around 500RPM (should never really hit that)
I did some calculations last year, I think I came up with 2k rpm min for fans without modifying ipmi tresholds.
2000 rpm becuase there are tolerances for max and low rpms.

The fan on that heatsink in the op has a rpm of 1600 +- 10% -> 1.440 ~ 1760 rpm max
30% pwm (impi default for optimal settings): ~432 rpm (1440), 528 rpm (1760)
With low rpm the tolerance goes up to 20%: lowest rpm with optimal settings and these fans ~345 rpm

Tolerances are listed in noctuas specifications for the fans.