The SAP HANA database holds the bulk of its data in memory for maximum performance, but it still uses persistent storage to provide a fallback in case of failure. After a power failure, the database can be restarted like any disk-based database and returns to its last consistent state.
To protect against data loss resulting from hardware failure, backups are required. Both native backup/recovery functions, an interface for connecting 3rd party backup tools and support for storage snasphots are available.
Backups save the payload (that is, the actual data) as well as the redo log. They are performed while the database is running: users can continue to work normally, and impact on system performance is negligible. For recovery, SAP HANA offers many different options, including point-in-time recovery.
Access additional resource: "Backup and Recovery" chapter in the SAP HANA Administration Guide.