When files are being accessed over the network, my fan is usually on high. The rest of the time the fan is always on low. Once in a blue moon, it will actually shut off, but that is very very rare. I don't have any of the servers enabled on it (iTunes, FTP, P2P, nothing).
If I disconnect the DNS-320 from the network, the fan shuts off after a few minutes!
I've tried different routers -- same result.
I've also tried disconnecting the only devices that access the DNS-320 (Apple TV & WDTV Live) from the network -- same result.
I'm really hoping the next firmware fixes this.