I recently had some troubles copying large files from my Windows PC over to the Debian Linkstation running an SMB share...
When doing it with windows explorer, it always showed the wrong free space on the hd i was copying to. Asking google for some time gave me a solution.
The problem is, that SMB always returns the space of the root folder your share points to. That means if you copy to "/somefolder/", in this folder a big hd is mounted for instance, then SMB will only recognize the free space of the root folder the samba share points to(for me it was "/").
A possible solution is that you create a samba share which points to "/somefolder/", then the correct disc space will be shown!
This can be done with a config file: "/etc/samba/smb.conf" for debian.
If you get access denied or wrong password entries, the user may not be added yet.
You can add new samba users with "smbpasswd" command.
Check "man smbpasswd" for details!
- a good samba overview can be found here:
http://www.brennan.id.au/18-Samba.html
Tip: Avoiding root account with samba is always clever.