1. Insert second disk in your server.
2. Enable disk mirroring.
3. Disable disk mirroring once the disks are synchronised
4. Store disk for emergencies.
Just bear in mind that the server licensing will check the disk identity if you change disks and may require you to re-activate the operating system in case you are trying to create a pirate copy using Ghost.
When creating an image using Ghost, the actual parameters you need to use, and the drivers required in WinPE, are often determined by the hardware you are using. So let us know what hardware you are running on, and whether the Server 2012 software was installed by you, or by the vendor.