I use Ubuntu 12beta on Lenovo Z575. I noticed that the disk spins down very quickly, few seconds after the last operation. And when I am working, e.g. in the vim and write quite often, it spins-up and -dow frequently, what is rather annoying (and causes the vim to freeze for a second...)
I used hdparm but it didn't change anything:
hdparm -S 24 /dev/sda # 2 minutes standby time
and I see (and hear) that the disk is idle or working:
hdparm -C /dev/sda
drive state is: standby
# or...
drive state is: active/idle
I have laptop-mode-tools already installed
