My first managed GigE switch, the Linksys SRW2008, was a dream, until it started randomly chattering on various ports. That started while I was on the road all the time, which made it take forever to diagnose, but that's a different problem. When I finally determined that the switch was bad, it was still covered by warranty by Linksys/Cisco, so I opened an RMA ticket and returned it.
Unfortunately, Linksys/Cisco "upgraded" my replacement switch to a SRW2008P, which has Power over Ethernet features I never planned on using. That by itself wasn't so bad, but it's my guess that the inclusion of PoE functions in this model required a tiny, super-loud internal fan to keep everything cool. This wasn't something I wanted or asked for, but, now that I am stuck with it, I am investigating options for replacing that little internal fan with something far quieter. For example, if I attach a larger fan to the outside of the chassis, I think it could push enough air to replace the stock fan that is currently there. Any advice on carrying this out? I have no interest in melting my switch due to insufficient ventilation.
Update
Quite a few Linksys customers are having the same problem with other models in the SRW managed switch family, so when I broadened my search to include the SRW2024P, I finally found some helpful advice on how to open the switch and replace the fan. After reading the forum posts and looking at some pictures of a disassembled SRW2024P, I used a nylon spudger and a few plastic gift cards to gently pry apart my SRW2008P's case. Wedged between a clip and a notch in the metal was a standard 40mm x 20mm 12V fan. It was hardly a surprise that the fan's data sheet listed a 20dB noise rating, which I presume gets worse after it's been running for a few years and the worn bearings are growling with resentment.
The good news is that significantly quieter fans are available in the same size for as little as USD$10. The IXP1314 iXtrema Pro from SilenX is a 40mm x 20mm 12V DC case fan that snaps nicely into the same notch where the old fan went, so there is no need to rework anything with a Dremel just to install a replacement fan. The noise level dropped quite a bit with the new fan, but I think I can make it even quieter by installing a "noise reduction" cable that uses a resistor to throttle the fan speed. I'm only considering this additional step because I never use power over ethernet or any other feature that would generate very much heat on the switch.
Best Answer
As you suspected, small fans and high RPM make for a high noise level. These fans aren't good at anything except making enough pressure to get air past obstructions. In choosing your cooling mod tactic, take a good look at the system and see if the tiny fan is blowing air on one particular component, or just drawing air out of the case in general.
Replacing the fan with a large, slow one is definitely an option, providing you don't mind voiding the warranty for the modifications required. In doing the change, keep in mind that slower fans don't build as much pressure, so you have to provide larger, more free flowing passageways. That means you'll probably need to remove some metal, make a large hole or many small ones, to increase the airflow. If you're blowing in, you'll need to carefully seal the edges of the fan against the case. Silicon hobby glue or gasket maker is good for this.
If you're drawing air out, you should use the natural convection tendencies of the system by putting the fan out top, blowing upward.
In the days of 80mm case fans, I modded every system case I bought to a.) provide as many fans in as out, and b.) replace as many 80mm fans with 120mm fans as possible, and c.) use lower RPM fans, and more of them. The result was always cooler and quieter then the original setup, even if the original had only two fans.