So I looked at what noctua proposed in its range, in fact, a lot of feedback indicated that NF-R8 were perfect. In seeking a little more, the R8 has been replaced by the A8, and even if the 18 are slightly less efficient (approx 53CFM vs 50 CFM), I opted for the 18 pusiqu'ils are newer and are more silencer 1 DB!
In short, once installed in the DS1515 +, I found a similar level of noise DS214 + I have and that works at the moment with a disc (disc only in the DS1515 +, the time to migrate and put into production :)
In short it is a bit expensive to change ventilos 2, but it's worth it when the NAS works in a room for example.
