Which requirement is essential for host auto-failover in SAP HANA?

For host auto-failover in SAP HANA, it is essential that standby hosts require access to all database volumes. This is crucial because auto-failover is designed to maintain the availability of the database in the event of a failure. The standby host must be able to access the same data that the primary host manages, which entails having direct access to all database volumes. This ensures that if the primary system encounters an issue and switches over to the standby, there is no data inconsistency or loss, allowing for a seamless transition to the standby host.

Other elements involved in failover, like geographic distance or transaction processing, might be considerations in specific high-availability setups, but the fundamental requirement revolves around the standby's capacity to handle the database volumes. This access enables the standby host to take over smoothly, maintaining service continuity and data reliability.