Friday, 25 August 2017

SAP HANA High Availability with Minimal Setup (a step by step procedure)

This blog gives you information about the minimal setup required for HANA high Availability. How to add standby host and perform a failover (simulation). How services, hosts and Volumes looks like before and after failover.

For high availability, a distributed HANA (scale out) setup is required.

The minimal setup for a scale out is 2 servers (one worker, one standby).

When an active (worker) host fails, a standby host automatically takes its place.

For that, standby host needs shared access to the database volumes.

Note: standby hosts do not contain any data and do not accept

requests or queries.

Host 1 (first node):

host role = Worker

host name = hanasl12

SID = HIA

Instance Number = 00

IP Address = 192.168.1.149

Host 2 (second node):

host role = Standby

hostname = hanadb4 (alias hanadb2)

SID = HIA

Instance number = 00

IP Address = 192.168.1.172

failover group = default

NFS is used here to shared file systems (/hana/shared, /hana/data/ and /hana/log)

export /hana from first node: /etc/exports

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SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

On second node: maintain /etc/fstab as shown below and mount the file systems.

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

Install SID= HIA, master node (first node) using installation media’s HDBLCM (the below screen shows services before adding standby node)

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Hosts:

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On master node: execute action configure_internal_network (using resident HDBLCM)

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

Then, on second node: run resident HDBLCM to add_hosts

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Select Host role as “standby”

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

The below screen, shows services after adding standby node

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Hosts – after adding standby node:

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Volumes: (before failover) attached to active (worker) – on first node

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To perform failover (simulation), I’ve killed deamon process

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The below screen shows, stopped first node and now second node has Master name server (actual role) and Master Index server (actual role)

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

Volumes: (After failover) attached to second node

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

start instance on first node, it retains standby role (as actual role).

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides

SAP HANA Tutorials and Materials, SAP HANA Certifications, SAP HANA Learning, SAP HANA Guides