Hello, newbie here. I also have just purchased a DS211 and the fan noise is stupidly loud. A droning sound similar to an idling two-stoke moped. Sometimes low, sometime higher pitched, depending upon the load. A royal pain.
Just for fun, I measured the dB(a) sound level, using the iphone - admittedly not a scientific test - and the result.....an' Leq' (average) of 47.8 decibels, (a) weighted. Now, that's not significantly loud in a busy commercial office environment, but it's almost 5 times as loud as the promotional blurb from Synology and in my home, where the DS211 needs to be left turned on all the time, it's far too noisy. Difficult to concentrate, when working in the same room and a gently nagging hum audible through the wall in the adjoining bedroom. Interrupting Sleep. For Me. And The Wife. (Very bad!).
In fact, I have a small conventional server at work that's quieter than the DS211. Compared to my previous Apple Time Capsule, (which was quiet, but prone to operating temperatures that could fry an egg), and compared to other NAS servers owned by acquaintances of mine, (older QNAP and Netgear), it's fan noise seems much, much louder. I have only owned this unit for a few days, and am now quite prepared to throw it out of the window.
So, I would like to know, before I take it back for a refund or replacement - Is this normal?
Are all DS211 units supposed to make this incessant humming noise? I have never owned a Synology NAS before so I don't know. Is it a faulty fan motor? Or a consequence of negligent design and marketing lies by Synology? Either way, I am not happy with the Synology DS211 and don't have time to mess around voiding the warranty to attempt to replace the fan - if indeed that is practicable. And, it might still make the humming sound after all that. Who knows?
As for Erik-a-Danish guy, I admire your perseverance to last 14 days before complaining. It must be driving you insane. I'm afraid I can't help you, as we are both in the same boat. However, my approach will be - 24 more hours to let the fan settle down - if it still hums - take out the hard drives and return the unit to the point of sale. If they don't accept it back, get the big hammer from the shed.....
DSM 3.0 seems such an easy to use operating system and I was looking forward to all the wonderful tricks the DS211 can perform - and kind of does already, but it doesn't matter if the hardware is unreliable trash.