[S.u.S.E. Linux] Hard disk led

Hy all, Most of the times I have my system running my harddrive led is on...not that I hear any disk activity. Only in a couple of times the led goes off. This obviously isnt a problem but I was just wondering...is this normal??? a bug??? Does anyone have info about this???? Thanks - To get out of this list, please send email to majordomo@suse.com with this text in its body: unsubscribe suse-linux-e