how to find out which program is using the harddrive

[Tamas K Papp <tpapp@Princeton.EDU>]

Even though I don't have sleep on my powerbook yet, I am OK with just
closing the lid and letting the screen sleep.  However, something is
using the hard disk about every 2 seconds...  How can I find out what
it is?  I checked the usual suspects (stopped the firewall from
logging everything, etc), checked the /var entries in the output of
lsof, now nothing changes there.  What else could it be?  Does
smartctld physically move the head when checking on the hard drive?  I
don't think so.

Tamas