[rescue] V100 fans

[Jonathan Patschke]

On Fri, 10 Feb 2023, vom513 via rescue wrote:

> Hopefully not too much of a tangental question for this thread - has
> anyone tried Noctua fans that all the kids nowadays are using ?  They
> have a reputation for being very quiet and not sacrificing airflow.

I use both them and Arctic fans as replacements in a variety of network
kit (UPSes, tape robots, SuperMicro "fan walls" behind drive
backplanes).

If you read the datasheets and to match specs to your application,
they're really, really good.  They don't have the lifetime of the
Delta-branded fans that tend to be in enterprise gear, but the
difference in noise output makes "rackmount" into "office friendly."

> I would worry about compatibility though.

With a fan, you only have to match:
     * Power (voltage, AC vs DC)
     * Dimensions (diameter and depth)
     * Tach/PWM lines, if present

Match all three of those, and the fan will plug in and do its job.  For
it to do the job *you* need, you need to match airflow (usually
expressed in CFM) to your application.  If you're running a switch with
all ports loaded, high traffic, and installed in a closet, you need the
full originally-rated airflow, and you'll need a loud fan to get that.

But since most of us run "home lab" setups, we can safely de-rate by a
bit.

The only compatibility I've hit so far is in a SuperMicro system where
the PWM curve of the fan doesn't match what the management firmware
wants.  When the machine gets cool, the PWM waveform off the backplane
controller spins the fan *too* slowly, which makes the firmware panic,
which makes it run the fan at 100% duty cycle, which keeps the machine
nice and cool, which causes the backplane controller to back-off and PWM
the fan down, ....

Thankfully, those values are tweakable via IPMI, which I can re-load
from /etc/rc.local each boot.


-- 
Jonathan Patschke
Austin, TX
USA