@Bob_Zimmerman makes a very good point. IF its standalone, then you could introduce whats called Full HA, which is essentially 2 standalone devices in a cluster. Then, you would have 2 gateways and 2 mgmt servers in a cluster...personally, not something I would recommend, as I always found when it works, works 100% great, but when it breaks, good luck fixing it : - ). Now, if your device is just a gateway, then you can introduce a new gateway to be part of a cluster. Just run commands he gave and you will confirm for sure.
Andy