PS3 Developer andbey0nd has released a Homebrew application that lets you switch [game data] locations, between internal and external, here is a quote from the source:
Today, we get word of a new amazing and very useful app called gameDATA tool, released by developer andbey0nd.
Also we hear from the Dev that this handy app should also work for 3.41 users.
gameDATA app for PS3:
• Allows the user to switch location of [game data] between internal HDD and first external USB HDD
•Allows to install PSN games (or any application/pkg) to external USB HDD
•Allows to get back to normal mode when you use “Ext. Game Data” option in multiMAN
•Allows saving space on internal HDD
Video thanks to manster.