"One HCX Network Extension configuration cannot use multiple HCX-NE appliances." From: Restrictions for Network Extension.
I would recommend using something like vSphere HA in conjunction with the appliance to minimize any failure downtime. To my understanding, this is preconfigured in VMware Cloud on AWS.
Thanks for your reply.
I'm aware of HCX-NE restrictions. For a productive environment, would you rely an entire L2 extension to a single appliance? That's my concern. How can I recommend this to customers and ensure them a robust solution. The same with cloud gateway appliance. You HLM will depend on a VM?
There is a new-ish, licensed, feature in R134 which allows for redundancy at the appliance level. Release notes can be found here.
With that said, L2 extension should really not be positioned as a permanent solution without very careful consideration.