Thank you Narendra.
Do you know which version onwards has started VAAI support?
Also if you look at this KB: VMware KB: Frequently Asked Questions for vStorage APIs for Array Integration upgraded VMFS-5 table says it will support ATS but fall back to SCSI-2.
I am confused with this statement, does this mean ATS will be completely unavailable for upgraded file system and goes back to SCSI-2 reserve and release commands (a.k.a SCSI-2 reservations) were used for reserving and releasing volumes.