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What's covered in this post:

  • Support for scale out with RHEL 8.4 batch-update 2 is available for customers as of Aug 10th. 

  • The Global SAP Tech Alliance Team is working on validation and certification support for HANA scale-up deployments.


Background

For more than two decades, Red Hat and SAP have partnered to deliver pioneering world-class solutions that are now at the forefront of open source digital transformation. The Red Hat Enterprise Linux (RHEL) High Availability Add-On, which is included with Red Hat Enterprise Linux for SAP Solutions, is an automated high availability solution that increases reliability and stability by eliminating single points of failure and minimizing unscheduled downtime in scale-up and scale-out SAP HANA, SAP S/4HANA, and SAP NetWeaver deployments. 

Automatic failover is triggered without external user intervention, helping to provide a high level of operational performance with minimal disruption that is designed to be secure, responsive and provide business continuity.

So how does SAP HANA Multi-target System Replication fit into all of this?

Customers are preparing for their transition to S/4HANA (next-gen SAP ERP). To achieve zero RTO (Recovery Time Objective), SAP has positioned SAP HANA Multi-target System Replication as HA (high availability)/DR (disaster recovery) architecture. 

SAP HANA Multi-target System Replication consists of 3 and/or more system replication systems located in either the same or different data centers, which are kept in sync through HANA System Replication (HSR). In this context, customers will not be using the HANA Host Auto-failover feature due to the absence of a standby mode, and HA/DR will be solely achieved through multi-target system replication.

Automating failover between 3 SAP HSR

To automate failover between 3 SAP HSRs (SAP HANA System Replication), customers will need to request support for multi-target system replication from a Red Hat pacemaker cluster. While multi-target support for a 3 system replication site is the goal, the implementation itself can be segmented into two phases.

The first phase is support for 2 sites of HSR, where the pacemaker manages the primary and secondary site, with another secondary site situated outside of the cluster. 

The second phase is support for 3 or more sites of HSR, with the pacemaker managing a  primary and two secondary sites.

Automating SAP HANA Multi Target System Replication in a Pacemaker-based cluster on RHEL

The basis of the setup is an automated HANA System Replication cluster with 2 sites in a scale out environment. See Red Hat Enterprise Linux HA Solution for SAP HANA Scale-Out and System Replication for more information. 2 secondary HANA instances are required, and all instances require the same amount of the following:

  • RAM

  • CPUs

  • Nodes

Scale out deployments require multiple nodes per HANA instance. See the SAP HANA Administration Guide for SAP HANA Platform for more information.

Additionally, 3 sites are required:

  • SITE 1 or DC1

  • SITE 2 or DC2

  • SITE 3 or DC3

The initial setup is as follows:

  • Replicate Primary Site 1 (DC1) to Secondary Site 2 (DC2)

  • Replicate Primary Site 1 (DC1) to Secondary Site 3 (DC3)

If the primary fails, the Secondary Site 2 (DC2) automatically becomes the new primary for Site 3 (DC3). Subsequently, when failover occurs, this solution ensures that the primary is switched to the 3rd site. If Site 1 ( DC1) fails, replicate the new Primary Site 2(DC1) to the Secondary Site 3 (DC3). If the Primary falls back to Site 1 (DC1), Site 3 (DC3) needs to be re-registered to Site 1 (DC1). See Automating SAP HANA Multi Target System Replication in a Pacemaker-based cluster on Red Hat Enterprise Linux (RHEL) for more information. 

Next steps

Support for HANA scale-up deployments is planned for the next release, complementing the current offering of scale-out deployment support for Multi Target Replication. Learn more about Red Hat Enterprise Linux for SAP Solutions and how Red Hat’s integrated SAP offerings provide a consistent, reliable and proactive enterprise-grade foundation for your workloads with the latest technologies. 

Additional Reading


About the author

Vivien Wang is an experienced Senior Technical Writer who specializes in the documentation of solutions for Red Hat Enterprise Linux (RHEL) on SAP in the partner ecosystem. Prior to joining Red Hat in 2019, she worked at SAP UKI, and as an in-house technical writer for ASUS and Mitsubishi Heavy Industries. She holds a master's degree from King's College London.