if you just want an identical partition, then you could just do:
# rsync -avl / /mnt/other_hd
this will preserve all the times and ownerships.
Note: you might want to do
# rsync -avl /bin /mnt/other_hd
# rsync -avl /boot /mnt/other_hd
and do each folder in / individually to avoid it copying the files from the /mnt/other_hd partition !
hope the backup went well.