Each installation of NSX-T requires and supports only one instance of NSX Manager. NSX Controller clusters should have three members. NSX Edge clusters should have at least two members.
If an appliance in a controller or edge cluster becomes inoperable, or you need to remove it for any reason, you can replace it with a new appliance.
If you make any changes to NSX Controller or NSX Edge cluster membership you must take a cluster backup afterwards to back up the new configuration. See Backing Up and Restoring the NSX Manager.