Constraints - SAP HANA on AWS
Cluster defaultsConstraint: start SAPHanaTopology before SAPHanaConstraint co-locate the aws-vpc-move-ip resource with the primary SAPHana resource

Constraints

Define two constraints, one for the Overlay IP address which helps with routing client traffic to active database host and the second one for the start order between the SAPHANA and SAPHanaTopology resource agents.

Cluster defaults

The following command creates the default cluster migration-threshold and stickiness for the cluster resources.

RHEL 7.x

[root@prihana ~]# pcs resource defaults resource-stickiness=1000
[root@prihana ~]# pcs resource defaults migration-threshold=5000

RHEL 8.x

For RHEL 8.0 through 8.3:

[root@prihana ~]# pcs resource defaults resource-stickiness=1000
[root@prihana ~]# pcs resource defaults migration-threshold=5000

Starting with RHEL 8.4 (pcs-0.10.8-1.el8):

[root@prihana ~]# pcs resource defaults update resource-stickiness=1000
[root@prihana ~]# pcs resource defaults update migration-threshold=5000

Constraint: start SAPHanaTopology before SAPHana

The following command creates the constraint that mandates the start order of these resources.

RHEL 7.x


[root@prihana ~]# pcs constraint order SAPHanaTopology_HDB_00-clone \
then SAPHana_HDB_00-master symmetrical=false

RHEL 8.x


[root@prihana ~]# pcs constraint order SAPHanaTopology_HDB_00-clone \
then SAPHana_HDB_00-clone symmetrical=false

  • symmetrical=false — This attribute defines that it is just the start order of resources and they don't need to be stopped in reverse order.

  • interleave = true — This attribute allows parallel start of these resources on nodes. This allows the SAPHana resource to start on any node as soon as the SAPHanaTopology resource is running on any one node.

Both resources (SAPHana and SAPHanaTopology) have the attribute interleave=true that allows parallel start of these resources on nodes.

Constraint co-locate the aws-vpc-move-ip resource with the primary SAPHana resource

The following command co-locates the aws-vpc-move-ip resource with the SAPHana resource when promoted as primary.

RHEL 7.x


[root@prihana ~]# pcs constraint colocation add hana-oip with master SAPHana_HDB_00-master 2000

RHEL 8.x


[root@prihana ~]# pcs constraint colocation add hana-oip with master SAPHana_HDB_00-clone 2000

You can use the following command to check the final status of the cluster: 

[root@prihana ~]# pcs status
Cluster name: rhelhanaha
Stack: corosync
Current DC: sechana (version 1.1.19-8.el7_6.5-c3c624ea3d) - partition with quorum
Last updated: Tue Nov 10 17:54:13 2020
Last change: Tue Nov 10 17:53:48 2020 by root via crm_attribute on prihana

2 nodes configured
6 resources configured

Online: [ prihana sechana ]

Full list of resources:

 clusterfence   (stonith:fence_aws):    Started prihana
 Clone Set: SAPHanaTopology_HDB_00-clone [SAPHanaTopology_HDB_00]
     Started: [ prihana sechana ]
 Master/Slave Set: SAPHana_HDB_00-master [SAPHana_HDB_00]
     Masters: [ prihana ]
     Slaves: [ sechana ]
 hana-oip       (ocf::heartbeat:aws-vpc-move-ip):       Started prihana

Daemon Status:
  corosync: active/enabled
  pacemaker: active/enabled
  pcsd: active/enabled
[root@prihana ~]#

This concludes the configuration of the SAP HANA cluster setup. You can proceed with testing.