[gentoo-user] Preserving the initial partionin/formatting of an usbstick

Hi,

since companies know their usbstick internals  best, they 
format their drives in a way, that the performance is best.

That's why I want to make a complete image "backup" of my
new usbstick first before using it in case of needing to
reset the whole thing.

The stick is a 64GB vfat formatted device.

How much of the usbstick do I need to dd/pv from
the stick to preserve *all* informations to do a 
"true factory reset" later if needed?

Thank you very much in advance for any help!
Best regards,
Meino