Drag & Drop vs mv - Any difference?
Do not use mv or drag&amp;drop for moving data between volumes.

If anything bad happens during the operation, you will end up with half the data here and half the data there, and it will be hard to figure out where to restart. If this is done over the network, you may not even still have all the data on either volume.

Do a copy (command line or drag&amp;drop), and after that succeeded, delete the source.