We copy LOTS of files to and from USB hard drives from our Linux servers. A common frustration of ours has been that the linux "cp -v" command doesn't copy files and folders in alphabetical order which makes it hard for us to be able to tell at a glance how much of the file copy process is complete.
Instead, we now use RSYNC to copy the files. The command "rsync -avP /source /destination" performs the same as "cp -Rvf /source /destination" plus it includes some nice progress stats too.
Maybe this will help you too.
Automatic and secure online backup

John Karran – Jeweller and Watchmaker, Karrans of Hyde Park
