To ensure optimal performance, SAP HANA database holds the bulk of its data in memory. However, it still uses persistent storage to provide a fallback in case of failure.
During normal database operation, data is automatically saved from memory to disk every 5 minutes. Additionally, all data changes are recorded in the redo log. The redo log is saved from memory to disk with each committed database transaction. If there is a power failure, memory chip or CPU issue, the database can be restarted like any disk-based database, and it returns to its last consistent state by replaying the redo log since the last savepoint.
While savepoints and log writing protect your data against power failures, savepoints do not help if the persistent storage itself is damaged. Backups are required to protect against the data loss due to disk failures. Backups save the payload (the actual data) of the data area and log area to different locations.
Backups are performed while the database is running. The impact of backups on system performance is negligible, and users can continue to work normally while the backup is running. Backups complement other availability strategies such as system replication and storage replication. Backups are also used for other scenarios such as database copies.
A full data backup contains all current data, while a snapshot saves the content of the whole data area. Snapshots are an alternative to full data backups. Delta backups contain data that was changed since an earlier data backup. Differential & incremental delta backups are possible.
Native backup/recovery functions and an interface for connecting 3rd party backup tools and support for storage snapshots, such as Hitachi Data Instance Director, are available within SAP HANA,. For recovery, SAP HANA offers many different options, including point-in-time recovery.
There are different options for carrying out backups for SAP HANA
1. Backup to the file system
2. Backups via the “Backup Interface for SAP HANA” API to 3rd party tools. 3rd party backup agent runs on SAP HANA server. Backups are transferred via pipes.
3. Certified backup tools (connected via Backint API).
4. Data snapshots using storage tools
Hitachi Protection Platform S2750 provides the features to support backup and recovery using Backint for SAP HANA with Veritas NetBackup. It is a backup appliance designed to deliver powerful, scalable and cost-efficient data protection storage for large SAP HANA databases.
Veritas NetBackup media server and master server performs backup of the SAP HANA database to Hitachi Protection Platform S2750. Install NetBackup Client software on all the SAP HANA nodes in the HANA cluster. After configuring the NetBackup master and media server with recommended settings for use with SAP HANA, configure the NetBackup client (HANA nodes) to integrate with the NetBackup server using Backint for SAP HANA.
When initiating a backup or recovery process, NetBackup for the SAP HANA Agent runs on the SAP HANA nodes. It communicates with the NetBackup servers through the Backint interface to perform backup or recovery tasks.
You can mix different backup options for taking data and log backups.
Data backups can be triggered using (applicable to Backint as well):
1. SAP HANA Cockpit
2. SAP HANA Studio
3. SQL commands
4. DBA Cockpit (scheduling)
Log backups are written automatically and also to Backint, if configured. For improved performance, Backint can now use multiple parallel streams for data backups.
Backint has the following advantages:
1. Consistency checks on block level
2. Additional features, e.g. encryption or de-duplication
3. Data center integration
4. Backups immediately available for recovery
When Backint initiates a backup or recovery task from SAP HANA Studio or an SQL statement, SAP HANA creates a data stream pipe. The SAP HANA agent that runs on the SAP HANA node communicates with the Veritas NetBackup servers through the Backint interface using these data stream pipes to perform backup or recovery processes.
NetBackup for SAP HANA Agent reads the data stream from these pipes and passes them to the NetBackup server, which then is saved to Hitachi Protection Platform virtual tape libraries.
Recovery is performed with the following phases:
1. Data recovery (full backup + delta backups + incremental backups, if applicable)
2. Log replay (log backups + log entries from the log area, if applicable)
3. Restart of database
When initiating a recovery task from SAP HANA Studio or an SQL statement, SAP HANA establishes communication with NetBackup for SAP HANA Agent using data stream pipes. SAP HANA requests the backup data from the Veritas NetBackup server, which reads the data from Hitachi Protection Platform virtual tape libraries. NetBackup for SAP HANA Agent then streams the backup data received from the NetBackup server through the data stream pipes to the SAP HANA services to perform the recovery.
Refer the Reference Architecture Guide for details on Backup and Recovery using Backint for SAP HANA with Veritas NetBackup on Hitachi Protection Platform, the UCP for SAP HANA Veritas NBU Appliance Integration Guide and the following SAP Notes for more details .