"No Log" is recommended for Application backups, like Oracle, SQL, Exchange. For File System backups, we usually recommend either Log Files or Log Directories. Before committing yourself to No Log for file system backups, make sure that you can do a Restore. Usually, when No Log is in effect for a file system backup, when you try to restore, you cannot expand your objects to see individual files and folders
I would suggest that you go to your GUI, click on Help -> Help Topics, and look up "Logging Level", there is a limited amount of information there