Are people still spinning down their harddrives?
I tried setting the harddrive in my laptop to spin down after 1 minute of inactivity, and noticed that the battery life has not lengthened significantly (didn't time it). I'm sure the drive was spun down, as I can hear the motor when it's running. When an application needs to access the harddrive when it's spun down, there's about a 3 seconds delay. Definitely noticeable. It needs to wake up once every few minutes, too, to commit the journal to disk.
I looked up the specs of my drive -
WD Scorpio Blue 320 GB SATA Hard Drives ( WD3200BEVT )
and it says -
(By the way, what's the difference between 5V DC and "power dissipation"? I have always thought P=IV, and it only doesn't agree for the "Idle" power)Power Dissipation
Read/Write 2.50 Watts
Idle 0.85 Watts
Standby 0.25 Watts
Sleep 0.10 Watts
I'm assuming idle means still spinning, and standby means spun down.
For 0.5W difference... I don't know. And then motors draw high currents spinning up, so there may be no power saving at all if spun up frequently enough! (just free lag)
I was surprised that by default, Ubuntu doesn't spin down laptop harddrives on idle. I'm beginning to see why.