There’s been a number of questions regarding disk cloning tools and dd has been suggested at least once. I’ve already considered using dd myself, mainly because ease of use, and that it’s readily available on pretty much all bootable Linux distributions.

dd is most certainly the best cloning tool, it will create a 100% replica simply by using the following command. I’ve never once had any problems with it.

dd if=/dev/sda of=/dev/sdb bs=32M

(add a “bs=100M conv=notrunc” and it could be much faster)
Be aware that while cloning every byte, you should not use this on a drive or partition that is being used. Especially applications like databases can’t cope with this very well and you might end up with corrupted data.