When using Private Browsing within Mobile Safari, is any data saved to the iOS filesystem? In previous desktop-based browsers that I've used, when activating their built-in Private Browsing mode I'm used to the fact that as soon as the Private Browsing window is closed, all of the tabs that were open during that session are immediately closed and cannot be re-opened. In iOS, however, the behaviour of Private Browsing in Safari seems slightly different in that even if Safari.app is killed from within the App Switcher and even after a full device reboot, the tabs previously opened within Private Browsing are still there.

So - my question. Is any data entered/saved during a Private Browsing session from within Safari saved to the iOS filesystem? Examples of data that I was thinking of would include form history, saved cookies, and visited links. Is this data then cleared when toggling Private Browsing off and then back on?
Safari on iOS uses Private Browsing per tab, meaning the "Private" button just shows you the mode. When you open a new tab your browser will create a session isolated from the non-private mode (containing cookies, history...). 

This session is temporary and will be deleted when you close the tab - not when you click on "Private".