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
On second node: maintain /etc/fstab as shown below and mount the file systems.
Install SID= HIA, master node (first node) using installation media’s HDBLCM (the below screen shows services before adding standby node)
On master node: execute action configure_internal_network (using resident HDBLCM)
Then, on second node: run resident HDBLCM to add_hosts
Select Host role as “standby”
The below screen, shows services after adding standby node
Hosts – after adding standby node:
Volumes: (before failover) attached to active (worker) – on first node
To perform failover (simulation), I’ve killed deamon process
The below screen shows, stopped first node and now second node has Master name server (actual role) and Master Index server (actual role)
Volumes: (After failover) attached to second node
start instance on first node, it retains standby role (as actual role).