You can't create a bootable volume on a NAS drive no matter what software you are using. You need a directly-attached drive for that (although it might be possible to boot from an iSCSI drive - I haven't actually tried that with OS X).
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Just chipping in to say Time Machine is Amazing. Used it several times, for a complete reinstall from back-up to the odd file. Other OS's may offer their own back-up options but Time Machine is bloomin' brill.