I was wondering about the best setup when working at home with a laptop.

When I am at home, I have switched the power scheme to Home/Office Desk. So, the turn off monitor is set to after 20 mins. The turn off hard disks is set to never and the system standby is set to never. But, for some kind of reason, I keep hearing the hard disk working on intervals such as every minute as if it would refresh itself. This is not like a task being executed. This is some kind of engine you could hear such as a prevention mechanism that would be effective in such circumstances. Should I change the turn off hard disks to a specific amount of time?