Generally a noise like this is from the power regulation circuits - higher load would equal more power draw, more stress on the power regulation, more noise. In some cases, it can mean that it is going to fail early, but it can usually just be ignored. -----Original Message----- From: Public [mailto:public-bounces@talk.mikrotik.com.au] On Behalf Of Andrew Lau Sent: Friday, 6 June 2014 1:29 PM To: Public@talk.mikrotik.com.au Subject: [MT-AU Public] Spinning disk like noise on RB951ui-2HnD Hi, I've got one of these little beauties (RB951ui-2HD) at my home for my QOS and L3 load balancing. I'm curious, only recently, when any traffic goes through the device at over 10Mbps there's a noise which sounds a lot like a spinning hard drive under heavy load. Has anyone noticed this/is this normal? I'm not overly concerned, just a little curious. Right now it's running PCC with failover like a champ, I'd only wish I could do PCC and PCQ.. CPU is not even going past 30% Cheers, Andrew.