I've been searching for this but I'm not having much luck.
Now that I've basically gone back to JBOD's in my system I find that seemingly random browsing folders hangs for a few seconds before showing its contents. I assume its because a harddisk has spun down and needs to wake up.
HDD sleep is set to 30 minutes. What I'm unable to find is whether that is 30 minutes of idle system time or actual disk usage?
Also, when I open a disk, it often shows the root of the drive instantly, but accessing a folder makes it hang for a few seconds. Is that how it works with a sleeping drive? Like the root of the drive is shown from cache so it doesn't wake the drive unnecessarily or something?
I wish I could see from a log when each drive sleeps and wakes up, or a simple program showing red or green for each drive indicating its active or asleep.