Ok, this is a pretty utilitarian post. I did finally get my 18W Server up and running; in fact, it’s serving this post! But I can’t really get to 18W unless the 2x 2T WD20EARS [amzn] drives I have in it for media storage spin down when not in use.
And I had a heck of a time making that work. hdparm -y would quickly spin them down, but using hdparm -S to set an idle timeout seemed to have no effect; I had been trying to use hdparm -S 241 to set a 30 minute spindown time, and I had no luck whatsoever. With the drives spinning, the server used more like 30W.
Mostly through trial and error, I found out that if you set a lower spindown timeout, i.e. hdparm -S 3, the drive will spin down in 10 minutes. So unlike most drives which follow the timeouts as specified in the hdparm manpage, this one seems to spin down in 10 minutes for low -S values, and never for higher values. I don’t know what the threshold is, but for now, hdparm -S 3 is doing the trick for me. After doing this, the drives finally managed to be idle most of the time, when not serving up media:
I also used the idle3-tools to turn off the idle3 behavior and save the drives from the massive load/unload cycles; I don’t know if that’s warranted or not, but I did it anyway.
On a related note: The Western Digital Red [amzn] “NAS-optimized” drives might actually use a bit less power than even the “Green” drives. They use 4.4W (vs 5.3W on the Green) for read/write, 4.1W (vs. 5.5W) for idle, and 0.6W (vs. 0.7W) for standby/sleep. (Comparing to the WD20EFRX and WD20EZRX models here). If one of the Green drives in the mirror goes, I might consider replacing it with a Red.