this is great info. THANKS!
For those that DO want the normal SM IPMI fan curve, but simply want it at a REDUCED curve (ie you still want IPMI to gradually up/down the fan speeds based upon temperatures its reads) there is a hardware option.
https://www.amazon.com/gp/product/B072M2HKSN/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
this noctura fan controller is EXCELLENT. (as usual with nocturnal). it allows you to have a physical dial to set your 4-pin pwm fan's speed. but whats unique about it- it also can take a 4pin fan connector (from MB) as INPUT, and then adjust fans connected to IT (the noctura) based upon the speeds the MB is telling that fan header to spin at. So in this configuration, the physical dial on this nocturnal fan controller acts as an OFFSET for your IPMI's fan curve.
Im using this exact setup on 2x , 2u x10 DRU-i+ setups where for some reason IPMI has the fans idle at 4600rpm (too loud), even though temps are low/normal. its working great to keep the idle fan speeds low/quite , but if needed for heat they can spin up (if MB/IPMI tells them to).
(ofcouse you can do this same thing with a script + ipmitool, as a few great ones have been written, but i was looking for something a bit more "permanent/solid" as ESXi does not have ipmitool, nor did i want to worry about a remote VM running a script against this remote box).
on caviet - it does seem to have a injection molded sata power connector (a quick google search for Sata power connector fire , will show why these types of injecton molded sata connectors can be dangerious). however i have been assured by noctura support, that they tested their connectors extensively (FWIW). I personally still soldered and heatshrink'd a normal molex connector onto the 4x of these units i have running in servers.
(one note on this reference doc, while this is stated, imo its not very clear- if you manually set/override the actual fan speeds (via first setting fan mode to full), then the ipmi controller will not adjust the speeds based on the temperature at all (ie no fan curve will be used, or rather the fan curve will be a flat line at whatever you set the PWM % to). I tried to test if you pass the high alert CPU temp threshold (ie ~95c , ) would reset back to the fan curve and kick the fans back to 100% , but i wasnt able to get my cpu hot enough. I just wanted to add this info incase others read it. (again this was stated in the article, so maybe it was just me)