I have not done this myself....but supposedly if you partition your drive you will end up with a bunch of free space in between partitions.
Some guy created 5 partitions and then used some other dick utility to check the drive structure, this is what he got:
Partition Map Apple_partition_map 31kb
Volume Type Dependent Apple_Driver43 28kb
SCSI Driver Apple_Driver43 28kb
Volume Type Dependent Apple_Driver_ATA 28kb
IDE Driver Apple_Driver_ATA 28kb
Custom Apple_FWDriver 256kb
Custom Apple_Driver_IOKit 256kb
Apple Patches Apple_Patches 256kb
Free Space Apple_Free 131MB !!!
HD1 Apple_HFS 32GB
Free Space Apple_Free 131MB !!!
HD2 Apple_HFS 12GB
Free Space Apple_Free 131MB !!!
HD3 Apple_HFS 3GB
Free Space Apple_Free 131MB !!!
HD4 Apple_HFS 30GB
Free Space Apple_Free xkB
So why is there such a big space between partitions?