Sadly this trick doen't work with the option search for "Storage - disk size".
You can search for it - and you get a result - but you can't add the column in the result view!
The normal computer overview can't show you the same information.
But sadly you can't search for anything in ocs 2.1.2 - this is only possible via GLPI or OCS-Inventory 2.6
i hope i clarified it a little bit.
Option 3 is to serach via mysql - but this is more complex.
Kind regards