High Availability & SAP HANA

High availability means that a secondary system can immediately
take over in case of a problem with the primary system, with little
down time and no loss of data. This is an automated process in most cases. Clustering software and shared storage are required to do this. In this chapter, we discuss high availability and what it means in an SAP HANA context.SAP HANA appliances are built for high availability. This is achieved due to redundancy — redundancy in the hardware, software, network and data center design.

SAP HANA provides several levels of defense against outages:

• Hardware Redundancy — The SAP HANA appliance has multiple
  layers of redundant hardware and network components such as
  redundant power supplies and fans, error-correcting memories,
  redundant network switches and uninterrupted power supply
  (UPS). The disk storage system uses striping to provide redundancy
  from disk failures. These redundancy solutions are in the
  design of the appliance and are fully transparent to the operating
  system and SAP HANA database.
• Software Redundancy — SAP HANA is installed on SUSE Linux
  Enterprise or Red Hat Enterprise Linux for SAP. The operating
  system is pre-configured and only contains the operating system
  features used by SAP HANA. Additionally, the SAP HANA software
  also includes a watchdog function which automatically restarts
  the SAP HANA services when needed.
• Data Persistence — SAP HANA is an in-memory database but persists
  data to disks to support system restart and recovery from
  host failures, with minimal delay and without loss of data.
• High Availability – A standby host can be used for failover in case
  of failure of the primary hosts.

Keep reading in The SAP HANA Deployment Guide by Bert Vanstechelman.

This book provides system architects, technical consultants, and IT management the tools to design a system architectures to deploy SAP applications on SAP HANA. Explore production and non-production systems, deployment options, backup and recovery, data replication, high-availability, and virtualization in detail. Dive into on-premise deployment options and data provisioning scenarios. Walk through scale-up and scale-out options and data partitioning considerations. Review the advantages and disadvantages of storage and system replication options and when to use each. Clarify how to leverage HANA for single node and distributed systems. Dive into a discussion on software and hardware virtualization. Compare the options available and guide your decision using flowcharts your organization can leverage to choose the proper technology for your environment and specific needs. This book enables readers to carefully evaluate and implement a well-considered SAP HANA scenario.

• SAP HANA sizing, capacity planning guidelines, and data tiering
• Deployment options and data provisioning scenarios
• Backup and recovery options and procedures
• Software and hardware virtualization in SAP HANA

Bert Vanstechelman is the founder of and principal technical consultant at Logos Consulting. He has more than 20 years of experience in SAP Basis consulting, running many SAP versions in combination with all possible databases and operating systems supported by SAP. Bert specializes in platform migrations, SAP release upgrades, and Unicode conversions.