For example: /floyd/home/my-data. But this means adding extra bash commands to "floyd run ..." (mkdir in order to create my-date in /floyd/home and cp in order to copy my mounted dataset contents to this new location).
Unfortunately, this is the only workaround that you can try at the moment. If you want to keep the command smaller, you can create a bash script with the commands that need to be executed.
cp -R /floyd/input/my-data /floyd/home
python train.py ...
Then you can launch the Job in this way:
floyd run --data ...:my-data --env ... 'bash train.sh'
Hope that helps.