Comment 643 for bug 59695

Hanno, I don't really remember, but I think back when I was investigating problems with my Samsung drive I found that iotop didn't show all the interesting values and was patching it to be more precise. Also, please be aware, that querying smart will always unpark drive heads, because smart values (I think) have to be read from special sectors on your drive. The same goes for ANY hard drive temperature monitoring (because they ALL have to query smart to get drive temperature), so remove hddtemp if you have it installed.

If you want your drive to stay parked longer try enabling laptop-mode (look at /etc/laptop-mode/laptop-mode.conf for details and don't forget to set ENABLE_LAPTOP_MODE=true in /etc/default/acpi-support). What you must be interested in is *_MAX_LOST_WORK_SECONDS, but it will work on AC only when you have ENABLE_LAPTOP_MODE_ON_AC=1. You might, just like me, find it a lot better for your drive to stay spinned down than to have it constantly working with disabled APM.