Chris Wahl of the Wahl Network comments:
Block storage has a long history of being a bit fussy when it comes to performance and scalability, especially when used by multiple servers as with VMware’s VMFS. To help mitigate some of the headaches of using shared block storage arrays, VAAI (vStorage APIs for Array Integration) was developed and implemented. VAAI has many different features, called primitives, that are supported by most all modern storage arrays (check the VMware Hardware Compatibility List for yours).
This is a great list of the primitives you’re going to be seeing more of soon in VMware. Especially if you are getting into the development side of integration.
Read more at: The Many Names and Aliases of VAAI Primitives