I'm used to wiping everything when installing a new ROM, but I would like to know if a nandroid restore automatically wipes out the partitions it is recovering.
When I run a restore, I see some messages saying it is "formatting cache" and "erasing boot before restore", but the rest of my partitions (system, data, .android_secure, etc) don't have any accompanying messages about them being cleared first.
Does a nandroid restore overwrite partitions, or does it merge the files with the current structure?
And in the interest of making this applicable to a wider audience, is the process different for different phones (some have extra partitions) or different versions of clockworkmod? Or is the process the same for everyone?