Re: VAAI comes under Storage API or vsphere API

VMware vSphere® Storage APIs – Array Integration (VAAI), also referred to as hardware acceleration or

hardware offload APIs, are a set of APIs to enable communication between VMware vSphere ESXi™ hosts and

storage devices.

Best resource to learn:

vStorage APIs for Array Integration aka VAAI - Yellow Bricks

http://www.vmware.com/files/pdf/techpaper/VMware-vSphere-Storage-API-Array-Integration.pdf