NetApp Volume Encryption (NVE)- encrypt before or after adding data

Hi,
We are migrating a lot of CIFS data into a NetApp FAS8300 HA solution from another storage system. We got a 10Gbit line between the systems. Some of this data (25TB) will be placed on NVE volumes. What is the best practice: 

1) Encrypt the volume before adding data? or
2) Encrypt the volume after data is added to the volume

Best regards

Kenneth