I want to know reference sites using nfsv4.

I want to apply acl to nas storage. Currently we use nfsv3. To apply acl, we upgrade the version into nfsv4.
EMC, NetApp vendors says there is few cases to apply nfsv4. I wonder whether that is true.
I can't find the cases of applying nfsv4 using googling. Could someone help me with nfs4 customer sites ?