If no replication is required, this will be enough. The "mdir" option is to configure a folder where the generated sequence file ids are saved.
..code-block:: bash
./weed master -mdir="."
If you need replication, you would also set the configuration file. By default it is "/etc/weedfs/weedfs.conf" file. The example can be found in RackDataCenterAwareReplication
Then, you can simply check "du -m -s /some/big/folder" to see the actual disk usage by OS, and compare it with the file size under "/data". Usually if you are uploading a lot of textual files, the consumed disk size would be much smaller since textual files are gzipped automatically.
Now you can use your tools to hit weed-fs as hard as you can.