The backend can be installed on a single server or two servers (multi-host). By default, all the running backend components are supervised by docker. Therefore, in the case of a possible outage, the state automatically converges and repairs itself.
Instana supports an active-active HA setup, by provisioning two backends you reduce the impact of an unplanned service outage on your premises. The Agent will be simply set up to report into both backends, this covers use cases where data redundancy and high available service continuity are required.
For information on how to configure the agent to send to both, see our docs on configuring multiple backends.