Slow SvMotion of thin disks over NFS

Guys,

i'm moving some 1,7 TB thin disks (basically empty as i have just created them) between NFS datastores (on the same NetApp box) and sVmotion takes ages (approx 1 hour).

Is it normal ? as i'm assuming the thin empty disks should be moved faster than this while even VAAI is enabled.

Any guess ?

Thanks, Daniele