I know one of this biggest wear-and-tear factors on hard drives is constantly starting and stopping, and I've heard (anecdotally) that once you get a hard drive spinning, it will pretty much keep doing that forever. So I'm trying to make some decisions about letting disks spin down.

 

I've found a few separate places that claim an idle drive will consume 4-6W and a drive under load will consume 9-10W. So I'll use the 10W for my price estimate.

 

I have electricity with time-of-use pricing; I pay 8¢/kWh for 108 hours a week, 13¢/kWh 30 hours a week, and 17¢/kWh 30 hours per week. That's an average electricity price of 10.5¢/kWh, but I'm just going to liberally round up and say I pay 15¢/kWh.

 

Five disks using up 10W each 24hr/day at an electricity price of 15¢/kWh would cost me a whopping $5.40 per month. So cost is definitely not an issue here.

 

Would I actually see any benefits if I set it so that my disks never spin down? What about if I set a spin down delay of a few hours? That seems like it might be a nice middle ground. If I need a disk at some point, I'll probably need it again within the next 2-3 hours, but if I haven't touched it in 3 hours, I probably don't need it at the moment.

 

What do others do with their disks? Does anyone have any strong opinions one way or another?

Personally, I let my drives spin down.  Cost per month isn't the major issue.  (Although depending upon what drives you have, by spinning it down, you would have saved enough money in the course of say 1.5-2 years to buy an additional one)

 

My analogy is always this:

 

An lightbulb will also last damn near forever if its left on (whether its incandescent or CFL or LED)  Why don't you do that?

In general, I agree with the "don't waste electricity" argument. However, the reason for time-of-use pricing in my area is because there are a ton of different electricity sources. During the off-peak hours (when the disks would be most likely to be spinning without anyone using them) something like 90% of the electricity comes from hydroelectric and nuclear power. The higher usage tiers are when they have to turn on gas and wind power, but during those times, the server is going to be in use anyway.

 

During the off-peak hours, the demand is so low that they are exporting the hydroelectric power to places that are far, far away, and they turn off the wind turbines because they create a surplus of energy that the grid can't handle. And I use so little energy already that the electricity cost portion of my bill (not including the flat distribution fee) has never gone over $11/month.

 

Plus, this is the worst case consumption scenario. 50 Watts 24/7 would be 438kWh per year. The more likely scenario (spinning disks not under load) would be half of that.

 

But you definitely do have a valid argument and I will also consider alongside any other pros/cons that others may mention!

I've always just shut my entire servers down when not in use. However, I am currently rebuilding and going to run them as just jbod chassis connected via 8088 cables. So I will be spinning them down. My Red's don't use anywhere near 4-6 watts spun down. I'm about 0.6 watts per drive according to my kilowatt meter. Now your drives may differ depending on what you have. But my 12 bay chassis sits at 21 watts with all drives spun down.