If this is a default installation of ESXi on local disks (1 disk/volume system) then your new disks have to be added as additional volumes/disks and you have to create an additional datastore or add the new volume as an extent to the existing datastore. Personally I wouldn't use extents in a local disk configuration.
To grow a datastore you need adjacent disk space. Since the default VMFS partition isn't the last one on the disk that isn't not possible.
André
Thanks André
The goal is to add a new HD for each host. i don't know why this is the way they want to do it, but it is.