What are the differences between FileSystemStorage and ExternalStorage ?
    On copy/cut actions, FileSystemStorage doesn't use memory : External storage stores files in a volatile var for copy/cut actions.
    
Is it easy to use FileSystemStorage ?
    Just add in your Field definition: **storage = FileSystemStorage()**.
    Just take a look at FSSItem example.
    Warning: Never use **myschema['myfield'].storage = FileSystemStorage()**. This example never initialize storage layers.

Does large file use StreamIterator ?
    Yes of course.

Can I use the same storage path for many Plone instances ?
    No you can't. FileSystemStorage maintenance doesn't work if many Plone 
    instances use the same storage path.

Which AT Fields can I use with FileSystemStorage ?
    FileField and AttachmentField of course then ImageField, TextField, StringField.

Can I modify content directly on FileSystem ?
    No it's dangerous, contents using FileSystemStorage are not notified 
    about filesystem modifications.
    
Does undo action works ?
    Yes, only for deletion. If you delete a content and undo its deletion you can recover data.

Does it works with ZEO ?
    Yes, if you use NFS.
