If you have installed the SDK/vcli, then under /usr/lib/vmware-vcli/apps/vm, there is a vdiskcreate.pl script:
./vdiskcreate.pl -vmname ora-test-r2 -server vc-dev-1 -filename "testing2.vmdk" -disksize 1024
Adding Virtual Disk on Virtual machine ora-test-r2 in the host XXX.
Virtual Disk created.