After setting up a SMB Samba share on my Raspberry Pi in Squeezeplug, the size of the mounted volume showed the size of the SD-card instead of the USB hard disk. To fix it, I had to change the setup for Samba. Here’s what I did to fix it.

pico /etc/samba/smb.conf

To get Samba to show the correct size of the volume mount, you need to change the path setting to point directly to the disk mount point. I mounted my disk to /mnt/hd1

[media_lib]
comment = Public
Folder path = /mnt
guest ok = Yes
read only = No

change the line:

path = /mnt

to

path = /mnt/hd1

Restart the Samba server with the command sudo service samba restart. Now the mounted volume should show the right size of your attached USB disk.