Adding second harddrive for squid
How to add second hard drive to PFSense v2.0.1-NanoBSD?
Some instructions are given here:
You would also need to edit the fstab to have the new drive mounted at boot time.
This is not a supported configuration however. It almost certainly wouldn't survive a firmware upadte.
Seems i need extra package (shellcmd) to mount the extra storage on embedded system. CMIIW.
No you shouldn't need that. Just edit the fstab so that it gets mounted at boot.
The shellcmd package only gives you easy access to the shellcmd option in config file anyway.