the backup isn't what's bootable. time machine just makes a (hidden?) folder on the hard drive and stores stuff there. there's absolutely nothing stopping you from installing OS X on a time machine backup drive.
I understand storing a bootable system complete with apps and documents on a hard drive volume and also backing up a Time Machine image to the same volume, but how do you keep the bootable system current if it's not the regular boot system?
I've always thought that Time Machine backs up to its disk image and cannot be used to update a spare bootable system. I used to use Super Duper to perform a scheduled update to a spare bootable system, but I've stopped doing that lately and rely exclusively on Time Machine for backups and Time Machine Restore to update the spare bootable system by replacing the spare bootable system with a more current one. Is there something I'm missing here? I'd love to be able to update a spare bootable system with Time Machine without using the Snow Leopard Install DVD.
