Hello Bazo,
If you have nothing in your application/Data.fs thn you ncan delete this files which is present inside your filestorage directory (rm -rf /opt/plone/zeocluster/var/filestorage/*) and re run your zeoserver in foreground mode(fg). It will be automatically created while to start your server and check.
As Patrick said, you only have some permission issue whith your data.fs file. Alos you can use chown.chmod command to manage the permission. once you have reset the permission you will not face any kind of issue.
After all, if you will still face any problem then let me know i will send you the proper installation procedure of plone 4/5