License Server Redundancy

As per November 2017, license server redundancy can be achieved through two options:

Storing licenses on a hardware dongle, that can be attached to a backup server in the event of hardware failure.
If dongle-free licensing is crucial, several license servers can be established, each holding only a share of the full license contingent. In this scenario, all license servers must be added to the client server search list.

Viz Licensing Administrator Guide