Multiple datastores in 1 hard disk

Hi,

I'm doing this as a experiment. I have a 40GB empty harddisk.

First, create a datastore, specify 10GB.

After that, try to create a new datastore again. The same harddisk won't show up to select.

But if I try to increase the datastore, it works. So this means I can't have more than 1 datastore in a harddisk.

Any idea why Vmware design it this way ?