Thanks for the reply and link. Looks like I'm fine with creating a 4Tb datastore with ESXI 5.5.
I presume with a larger datastore, I should use a larger block size of 4mb or 8mb when I create and not the default of 1mb.
VMFS5 and later use a unified block size of 1MB independent of the size. There's not need (actually not even an option) anymore to select block sizes as with VMFS3.