SAP HANA is an in-memory database, which means the data is kept in the RAM of one or more SAP HANA worker hosts (active components that accept and process database requests).All database operations (reads, inserts, updates, and deletions) are performed in the main memory of the host. This feature differentiates the SAP HANA database from traditional databases, where only a part of the data is cached in RAM and the remaining data resides on disk.
Persistent storage enables you to restore the SAP HANA database to its most recent committed state in the event of failure. The log captures all changes by database transactions (redo logs). Data and undo log information are automatically saved to disk at regular savepoints (the default is five minutes).
As certified enterprise storage systems for SAP HANA, PowerStore storage systems can be used for both single-host (scale-up) and multihost (scale-out) systems in TDI deployments.
In single-host environments, the database must fit into the RAM of a single server. Single-host environments are preferred for online transaction processing (OLTP)-type workloads such as S/4HANA and SAP Business Suite on SAP HANA.
In multihost environments, the database tables are distributed across the RAM of multiple servers. These environments use worker and standby hosts. The worker hosts accept and process database requests, whereas standby hosts are passive components that have the database services running but no data in RAM. A standby host waits for a worker host to fail and then takes over its role, a process known as host autofailover. Because the in-memory capacity in these deployments can be high, scale-out SAP HANA clusters are perfectly suited for online analytical processing (OLAP)-type workloads with large datasets such as SAP Business Warehouse on SAP HANA and BW/4HANA. By default, SAP supports scale-out deployments of up to 16 worker hosts. If more than 16 worker hosts are needed, a site-specific SAP certification is required.