If there are no special circumstances, your OS SD card should be used to host the files. Check
And yes, you will have to expand your rootfs, there is a nice post about that...should be among these (sorry, didn't find it at first glance, but every tutorial I looked at does basically the same)
You have to, basically, only change the partition table (you do that ON the Pi, WHILE the Pi is running ;-) )
Good Luck!
/opt/piratebox/share/Shared
And yes, you will have to expand your rootfs, there is a nice post about that...should be among these (sorry, didn't find it at first glance, but every tutorial I looked at does basically the same)
You have to, basically, only change the partition table (you do that ON the Pi, WHILE the Pi is running ;-) )
Good Luck!