Could be useful remember workflow to connect external storange on ESXi 4.x/5.x and let it recognize from Virtual Machine hosted.
Here you can view relative workflow to enable this feature:
update 2014/04
USB support in ESXi/ESX 4.1 and ESXi 5.x (1022290)
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1022290
