Unfortunately, that will not give you a bootable mirror image of SSD1. Of course, If you don't mind rebuilding in case of a failure or corruption....
Actually when using TimeMachine on a Mac, or something like Acronis TrueImage Home or StorageCraft ShadowProtect it gives you constantly updating backups, so what you recover is minues/hours old rather than days/weeks/months. You can even use the Windows 7 backup functionality the same way. A backup is only as good as how automated it runs.
The question of mirroring or cloning a OS drive is what are you trying to protect against? Failure is pretty uncommon, but things like ransomware or accidental deletions are far more likely. HDD1 can be an external USB3 drive even.
Offline backups are great for files, but for OS drives, it's kind of pointless unless you are in a time sensitive industry where you have hot spare desktop computers ready to go. Only time I'd clone an OS drive would be for an OS upgrade, but I'm more a wipe and clean install kind of guy.
-Joe