[support] Why doesn't Drupal sees the "files" folder?

[dondi_2006]

AjK wrote:

> > Is there really no way to have separate files folders,
> > one for each virtual site?
> I set the files folder in the settings.php file thus:-
> 
> $conf = array(
>   'file_directory_path' => 'files/www.example.com'
> ); 
> so it can't be changed by a site admin

Thanks. Can it be changed to be inside the "sites" subfolder:
'file_directory_path' => 'sites/www.example.com/files'

this looks cleaner to me, since it would make per-site independent backups and, maybe, future migration of each
site to a separate server easier. What do you think?
Is it possible to set it as I propose? Is it a good idea?

TIA,
D.
say, future