Target disc mode for the iPad. How?

I want to back up my iPad by cloning the disc image like I do with Carbon Copy Cloner for the Mac. How do you bring up the iPad in target disc mode (or whatever term is used for it if different)?

Apparently most Apple forum 'power users' don't even know there's a hard drive in their computer (emphasis on 'users' I guess) so it's just not possible to even get this question across on that forum. Frustrating...

You don't, without jailbreaking it.

Go on...
I don't care the method or terminology used.

Can I ask why you'd want to do that? It seems like the hard way to do things.

Doesn't iTunes back your iPad stuff up when it syncs?

Theoretically. Every time I've tried to sync my PDFs and books they get sent hither and yon. Along with all their custom titles, etc. It's like Lucy with the football for me.

iOS stores files differently than a regular computer. When you copy files to your iPad via iTunes, they can generally only be accessed through apps that know they're there (and iTunes).

If you jailbreak your iPad, you can install a third party file browser like iFile that will let you see the full file system of the device. Even then, you won't be able to plug your iPad into a computer and just have it show up as an external hard drive (I think - it's been awhile since I jailbroke any iOS devices).

If you want to just be able to back up everything en masse, get an Android tablet. That kind of functionality just doesn't exist in iOS.

What kind of content are you trying to back up?