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 Post subject: Lowering fan noise by cutting away exhaust mesh ?
PostPosted: Wed May 23, 2018 1:22 am 
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Hi,
I have recently converted an old FD Define R3 case to a FreeNAS homeserver and stuck it in the cupboard. It is pretty much idling all the time but the cupboard, case and six WD Reds proved a bit more of a challenge than I thought, so I have turned up fan speeds a bit. That of course creates more noise. The fans are all new, and I would prefer not going down the route of buying new ones. I am also doubting whether I would gain more silence doing so.

At 30%-50% duty cycle the noise level is quite fine for a cupboard server, but now during summer I seem to need 70-90% duty cycle at least, and that creates more noise.

So, my thinking is that much of the noise when speeding up the exhaust fans comes from the metal mesh that the air has to pass through. What if I simply cut away the metal mesh so the the fans would pull out air through two open holes instead of meshed openings? I presume the airflow would be improved, but am I likely to remove noise? (Whenever I have tried a fan outside the case they have sounded very "calm swooshing", whereas if I stick them on front of a mesh it seems the pitch goes up several notches.)

  • Exhaust : 2 x Scythe Slipstream PWM 120mm
  • CPU : BeQuiet Silent Wings 2 PWM 120mm (came with PureRock cooler)
  • Intake : 2 x Fractal Design X2 GP-12 120mm, 1200rpm, but due to some hickup in the fan headers of my Supermicro board they run at 2400rpm. (these fans are 3pin and stay at this rpm all the time, but at lower duty cycles they are not a problem, hence I am looking at the exhaust to lower noise at higher duty cycles)


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 Post subject: Re: Lowering fan noise by cutting away exhaust mesh ?
PostPosted: Wed May 23, 2018 5:29 am 
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Joined: Tue Nov 02, 2004 12:22 pm
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Location: Guatemala
First, not sure what its cupboard server, can you explain a little more?

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At 30%-50% duty cycle the noise level is quite fine for a cupboard server, but now during summer I seem to need 70-90% duty cycle at least, and that creates more noise.
Most servers sit at idle most of the time, unless you doing heavy vitualiztions, not sure why you need such high fan %. Fractal fans around 70% are reaching close to 1k rpms so there is no escaping it, i have yet to find a very quiet fan driven at 1k rpms, usually the sweatspot for me at the most is around 800rpms, where they are quiet but noticeable.

Quote:
What if I simply cut away the metal mesh so the the fans would pull out air through two open holes instead of meshed openings?
Any restrictions to the air path will create noise, specially very heavy fan filters or very tight openings. With this in mid, honeycomb mesh like most common on the back of the cases, is one of the most efficient and less restrictive of the designs, wire grills are a little better in my experience but not by much, better would be nothing at all, but how much it improves depends on each setup and fans speeds. I would recommend to read Effects of Grill Patterns on Fan Performance/Noise.

Now what you can do is turn them off (for a brief time), i mean the exhaust fans and see if thats the noise that its bothering you just to be sure its not something else before comitting into moding.

Another thing is that i think you have your fans way up than you need them to be, even premade servers like Synology have 2x92mm fans to cool 8 hdds and they dont need to spin up to 1k rpms always. I think you need to test each slot and see the impact on temperatures on each component. Maybe the R3 is too restrictive for your purpose? try also to take the frontal filter and openning the door to see what impact you get with your testing.

I would also get an external fan controller, to tweak each fan individually, usually Supermicro motherboards have very lowsy bios fan control, if im not mistaken and all things remain the same, you can only control FANA and FAN1/2/3, limiting a lot what you can do individually.

I still don't get why you need the fans so high, maybe you could explain a little more what temperatures are driven you to increase the fan curves so much?

Now the easiest way would be to move it, thats the beauty of severs, in most cases they dont need to be near you.

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 Post subject: Re: Lowering fan noise by cutting away exhaust mesh ?
PostPosted: Wed May 23, 2018 6:46 am 
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Joined: Mon Sep 20, 2010 12:07 am
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Location: Atlantic Ocean
Hi,

A "cupboard server" is in my own terminology a server placed in the kitchen cupboard as opposed to in the closet or in the basement. I live in a small flat, and that is basically my only option, if I don't want to listen to it all day long and night.

I guess it is the ventilation in the cupboard that makes the situation a bit challening meaning that air is circulated, heated up and remain inside the cupboard until I open the door (which I plan to do, but is not always realistic, e.g, when eating at the table below, or reading the morning paper.)

Currently we are hit by a heatwave in Sweden and we have 25-28 degrees Celsius outside, and around 28-29 ambient around the case in the cupboard as a result. The heatwave saw my disks going up from 34-35 degrees to 37-38 and even full speed on fans could not bring those temperatures down. During long SMART test my hottest disk hit 41 degrees. This had med scared. I want to stay under 40 degrees, preferably with a bit of margin.

After starting this thread I did open the case door and the small door in front of each intake fan, exposing the fanfilters. I got much better flow as a result and with exhaust/CPU duty cycle set at 70% the disks are now 35-36 degrees which is a good temperature for me but the PWM fans sound a tad too much for my being able to smile proudly when my partner asks me sternly what I'm up to. :-)

I will certainly disconnect fans on and off to see which ones are the most disturbing ones, but as you can see from the placement of the server, it is a bit cumbersone so I like to have my thinking straight before going up there and pulling on those fan cables. Since the intake fans are fixed rpm and not a problem at low duty cycle for the PWM fans, and the increased duty cycle leads to the increased noise, I feel pretty certain that it is the exhaust/CPU fans that are the main culprits. The fixed rpm fractals could be the source of a mild coilwhine though, so I will look at them too... :-)

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 Post subject: Re: Lowering fan noise by cutting away exhaust mesh ?
PostPosted: Wed May 23, 2018 9:18 am 
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I get why you want to keep it in the cupboard, but you are just recirculating hot air and making the problem worse. I'm not familiar with that case, but users have found creative ways to softmount multiple drives in a case, with a lot of airspace between each drive, so that less airflow is needed to cool them and their mechanical noise is not transmitted to the case chassis. One guy did it with knotted bungee cords.

If I were you, I'd take it out of the cupboard and try to improve the cooling: larger spacing between drives, less restrictive intake/exhaust paths, maybe (slow) fans blowing directly on the disk arrays. I think you could get it quiet enough that it won't bother you, so you won't feel the need to hide it in the cupboard. You may need a different case or to mod the one you have.

As an aside, 40C drive temps are nothing to worry about. Google did a huge hard drive study (and others have too), that showed people are too focused on that. Humidity is usually a bigger factor in drive failure, for instance. I wouldn't really worry until closer to 50C.

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 Post subject: Re: Lowering fan noise by cutting away exhaust mesh ?
PostPosted: Fri May 25, 2018 6:40 am 
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Joined: Mon Sep 20, 2010 12:07 am
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Location: Atlantic Ocean
So, here is what I hope will consitute an epilogue:
I turns out that opening the door of the R3 case was so efficient that it proved much of the solution to my problems. Temperatures went down 2-3 degrees Celsius. I could lower fan duty cycle to 40-50% (500-700 rpm) and still stay around 36 degrees :) . This, however, made me notice coil whining from the overspinning fixed rpm fractals :x so I decided to cut the ambivalence short and went off the the store and bought me a couple of NF-F12 PWM since they sported (on paper) very high static pressure which could come in handy in front of the HDDs. I always thought there was a bit too much hype around Noctua, but I must say I am pleased with these fans... :oops:

I am aware I am recirculating hot air in the cupboard, but that is still preferable to placing the server anywhere else (small apartment). When I joined SPCR in 2010 I did test "bungymounting" the drives in mid-air with elastic string, but I found that it is actually the drives themselves that make the most noise from spinning, rather than their vibrations. I'll keep the case in the cupboard for the time being and will try to let in fresh air as often as possible.

So at the end of the day I will not have to cut out the mesh... :lol: :lol: :lol:

Thanks @Abula and @flyingsherpa for your input.


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 Post subject: Re: Lowering fan noise by cutting away exhaust mesh ?
PostPosted: Tue May 29, 2018 4:40 am 
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Is there air flow into / out of the cupboard / closet?

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http://neilblanchard.blogspot.com/


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 Post subject: Re: Lowering fan noise by cutting away exhaust mesh ?
PostPosted: Tue May 29, 2018 7:21 am 
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Joined: Mon Sep 20, 2010 12:07 am
Posts: 56
Location: Atlantic Ocean
NeilBlanchard wrote:
Is there air flow into / out of the cupboard / closet?


No, not other than through the door. I try to keep it ajar as often as closed, and during night I sometimes leave the door wide-open to circulate new fresh air into the space.

I installed a custom fan script for the FreeNAS that keeps all drives at 36-37 degrees Celsius even during prolonged (12-hour) file copying to the server with the door closed.


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