Hi theire,
If i'am right normally it's included in Compare vSphere Editions: Server Virtualization & Cloud Infrastructure | United States (Enterprise)
But what do you get on the Datastore through the VI-Client on the "Virtualization Acceleration" Tab? Supported or Unknown or other?
Problem is that it's also Firmware Dependend on the storage Boxes what VAAI methods are working and which one not.
some working with "ATS-only" and other ones still needs SCSI lockings.
have a look also please to
for example > on the Vi Client overview you maybe could see "supported" for VAAI 
> but in the background not every Function is supported.
theirefore you have to place
"esxcli storage core device vaai status get"
on the esxi.
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For example we have CX4 and i saw "supported" but the "Delete Status" was unsupported.
you should also have a look to the Matrix: (hopefully i got you're correct ISCSI Storage) > this info should be comfirmed by the storage Vendor > so because all the Info what Vmware is having > they get it from Storage Vendors. (and it could be that the Matrix is not the Latest Status on vmware site) > it's a way to Start with .
VMware Compatibility Guide: Storage/SAN Search
Best regards
Max