What is the real big advantage of spinning down drives? Cost? When you add up the total cost you can save on a monthly basis, it might come to like $2.00 or less. Noise? Well, if it is noise then your server is in the wrong spot. Move it to a closet or in the basement. I really think when a drive is constantly powered down / powered up takes more out of it then just spinning at idle.

I've had my server for almost 4 years now. I switch out drives about every 1-2 years when the next "double" of space comes out and price drops down to around $0.03-05/GB. Failures have not been an issue for me because the wear on the drives hasn't been a concern. I usually sell my drives as I finish with them and can be quite the stickler on eBay when it comes to what I get from them (I don't lose much  ).

 

Now back to your original statement regarding savings due to spin down. Lets say my server only saved $2.00 per month due to spin down. Now lets multiply that by 12, for 12 months in a year. Now lets multiply that by 4 due to how many years I've had my server. That's $96 I now have that I would not have due to electrical costs. I don't know about you, but that's free money to me right now and it seems worth it since I have to do absolutely nothing to keep it. Whether this is the amount of savings I get... I do not know. What a full server gets at at least 22 drives... I have no idea either. Regardless, under the settings of your original scenario, that totally seems worth it to me. $96 is $96.

my 2 cents on this subject is i have a heat issue sometimes in my country and this definitely does help to keep it a little bit cooler

as the drives are also in a 5x3bay which does have fans on it but they are so closely packed together it does not seem to help especially when the wind is just a hot wind.

 

 

unRAID gives you the option to set your spin down timer to 'never' if you don't want your drives to spin down.  Most people do want them to spin down for the reasons already given - reduced power consumption, reduced heat production, and in some cases, reduced noise.  Many people use their servers as data archives - the data is rarely read, therefore the drives are rarely spun up.  On my personal server, I make an effort to organize my data so that some drives spin up daily and other drives only spin up weekly or even less frequently than that.

Good call on the heat I forgot to mention that. Not only would that help with longevity it would also benefit in lower costs too due to wasted energy in heat.