The Linkstation is amazingly quiet, at least the PPC-based models like the LS1. After one year or two years of operation however, the LS fan may make some buzzing noise.
For some users, it was enough to oil the fan axis. Unfortunately you have to disassemble the LinkStation for this, You don't have to remove the circuit board but it might help. Carefully lift the panel out and you can see the fan which is held in on some springy plastic fingers. Ease them apart and you can lift the fan out. The wires are not too long so it is a little fiddly.
Next, using a Stanley knife, carefully peel back the label from the fan to expose the bearings. Don't damage the label, it is used to keep the bearings covered. Now apply a drop of lubricating oil, 3-in-1 oil works.
A contributor from Australia used a few drops of WD40 under the label of the fan - WD40 is typically used to lubricate and dry out car engine parts - and he reports a dramatic reduction in fan noise.
- I have my doubts about WD40 usage. I very much believe that there is an immediate reduction in noise. However, WD40 is a very bad long-term lubricant. It dries. It becomes sticky itself. It does not resist heat. WD40 is good for protecting non-moving parts from corrosion, for making stuck parts movable again and for cleaning parts. But after cleaning a moving part the part should be lubricated with some proper long-term lubricant. My choice would be a synthetic bearing oil. I would not use WD40 (at least not alone) for fear of ruining the fan in the long term.
Also you can pack the bearing area with some LB10 grease using the tip of a screwdriver. Wipe off any excessive oil/grease and stick the label back on. Assembly is the simply the reverse.
Some other users had to completely replace the fan, or wanted to replace their (LS2) fan with a more silent model. The stock fan is a 40mm x 10mm 12V fan, ADDA part #AD0412LX-G76. It can be replaced with most any equivalent fan. It may be easier to get the three pinned smart fans so that the system wont lock up.  
The fan speed can be controlled as well. Several scripts were made some time ago which sent commands to the AVR, however the custom ppc_uartd and mc_ctld replacement (avr_evtd) is capable of controlling the fan as well.
- Kuro Box User Community Forum Index -> General Talk : Replacement Fan?
- http://www.addausa.com/model_index.htm for more information
- The Linkstation Community Forum / Linkstation 2 (mips) / Replacing Fan
- The Linkstation Community Forum / Linkstation 2 (mips) / how to remove fan
- http://tech.groups.yahoo.com/ LinkStation General: Replacing the fan
- kuroboxwiki:Fan Control
- Cool and Quiet Scripts from Yahoo groups - Linkstation General Files
- AVR watch-dog daemon for Linkstation