Thank You for the answer...the problem is that sometimes (so not always) I hear a cute sound from hdd. I have 2 hdd WD60EFRX, at one of two, I have disabled the parking heads after idle timer. When I will have possibility, I'll disable the idle timer also for the other hdd. However, the next time that I turn-off helios64, I'll make a video and I'll share it here.