[CentOS] Constant disk activity

>Is there any way of finding out what is accessing the disk? Not only it
>shortens battery life, it is annoying while working in a quiet room.

When I had problems with irritating disk noises on a laptop it turned
out that the problem wasn't so much disk access as an over-aggressive
power management setting.

   hdparm -I /dev/hda | grep 'power management'

should tell you the current setting.  The default value seems to be 128,
but what exactly that means depends on your hard disk.  I found that
changing the setting to 200 was a big improvement:

   hdparm -B 200 /dev/hda

You can make the change permanent by editing /etc/sysconfig/harddisks.

Ron