Compare the outputs of ls -lh versus *du -sh ** when in the Virtual machine directory. In the following example the whatami-flat.vmdk is this so ls -lh shows the size as 10GB whereas du -sh * shows the size as 1MB (I created it as a test). A little clunky but it works.
root@esx 2000ADrouter# ls -lh *
<SNIP>
-rw------- 1 root root 10G Mar 9 10:52 whatami-flat.vmdk
-rw------- 1 root root 400 Mar 9 10:52 whatami.vmdk
root@esx 2000ADrouter# du -sh *
<SNIP>
1.0M whatami-flat.vmdk
64K whatami.vmdk
