Cluster resources - SAP NetWeaver on Amazon
Start clusterCheck statusPrepareCluster bootstrapSTONITHFile system resourcesOverlay IP resourcesInstance resourcesResource constraintsActivate cluster
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Cluster resources

This section covers the following topics.

Enable and start the cluster

This is applicable to both cluster nodes. Run the following command to enable and start the pacemaker cluster service on both nodes.

pcs cluster enable --all
rhxhost01: Cluster Enabled
rhxhost02: Cluster Enabled


pcs cluster start --all
rhxhost01: Starting Cluster...
rhxhost02: Starting Cluster...

By enabling the pacemaker service, the server automatically joins the cluster after a reboot. This ensures that your system is protected. Alternatively, you can start the pacemaker service manually on boot. You can then investigate the cause of failure. However, this is generally not required for SAP NetWeaver ASCS cluster.

Check cluster status

Once the cluster service pacemaker is started, check the cluster status with pcs status command, as shown in the following example. Both the primary (rhxhost01) and secondary (rhxhost02) servers should be seen as online.

pcs status
Cluster name: rhelha

WARNINGS:
No stonith devices and stonith-enabled is not false

Cluster Summary:
  * Stack: corosync
  * Current DC: rhxhost01 (version 2.0.3-5.el8_2.5-4b1f869f0f) - partition with quorum
  * Last updated: Tue Jan 10 21:32:15 2023
  * Last change:  Tue Jan 10 19:46:50 2023 by hacluster via crmd on rhxhost01
  * 2 nodes configured
  * 0 resource instances configured

Node List:
  * Online: [ rhxhost01 rhxhost02 ]

Full List of Resources:
  * No resources

Daemon Status:
  corosync: active/enabled
  pacemaker: active/enabled
  pcsd: active/enabled

Prepare for resource creation

To ensure that the cluster does not perform any unexpected actions during setup of resources and configuration, set the maintenance mode to true.

Run the following command to put the cluster in maintenance mode.

pcs property set maintenance-mode=true

Cluster bootstrap

Configure the cluster bootstrap parameters by running the following commands.

pcs resource defaults update resource-stickiness=1
pcs resource defaults update migration-threshold=3

Create fence_aws STONITH resource

Modify the commands in the following table to match your configuration values.

pcs stonith create rsc_aws_stonith_RHX fence_aws region=us-east-1 pcmk_host_map="rhxhost01:i-xxxxinstidforhost1;rhxhost02:i-xxxxinstidforhost2" power_timeout=240 pcmk_reboot_timeout=300 pcmk_reboot_retries=2 pcmk_delay_max=30 pcmk_reboot_action=reboot op start timeout=180 op stop timeout=180 op monitor interval=180 timeout=60
Note

The default pcmk action is reboot. If you want to have the instance remain in a stopped state until it has been investigated, and then manually started again, add pcmk_reboot_action=off. Any High Memory (u-*tb1.*) instance or metal instance running on a dedicated host won't support reboot, and will require pcmk_reboot_action=off.

Create file system resources

Mounting and unmounting of file system resources to align with the location of the SAP services is done using cluster resources.

Modify and run the following commands to create the file system resources.

ASCS

Use the following command to create ASCS file system resources.

pcs resource create rsc_fs_RHX_ASCS00 ocf:heartbeat:Filesystem device=<nfs.fqdn>:/RHX_ASCS00 directory=/usr/sap/RHX/ASCS00 fstype=nfs4 options="nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2,noresvport" force_unmount=safe --group grp_RHX_ASCS00

ERS

Use the following command to create ERS file system resources.

pcs resource create rsc_fs_RHX_ERS10 ocf:heartbeat:Filesystem device=<nfs.fqdn>:/RHX_ERS10 directory=/usr/sap/RHX/ERS10 fstype=nfs4 options="nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2,noresvport" force_unmount=safe --group grp_RHX_ERS10

Notes for ASCS and ERS

  • Review the mount options to ensure that they match with your operating system, NFS file system type, and the latest recommendations from SAP.

  • <nfs.fqdn> can either be an alias or the default file system resource name of the NFS or FSx for ONTAP resource. For example, fs-xxxxxx.efs.xxxxxx.amazonaws.com.

Create overlay IP resources

The IP resource provides the details necessary to update the route table entry for overlay IP.

Modify and run the commands in the table to create IP resources.

ASCS

Use the following command to create an ASCS IP resource.

pcs resource create rsc_ip_RHX_ASCS00 ocf:heartbeat:aws-vpc-move-ip ip=172.16.30.5 interface=eth0 routing_table=rtb-xxxxxroutetable1 op monitor interval=20s timeout=40s --group grp_RHX_ASCS00

ERS

Use the following command to create an ERS IP resource.

pcs resource create rsc_ip_RHX_ERS10 ocf:heartbeat:aws-vpc-move-ip ip=172.16.30.6 interface=eth0 routing_table=rtb-xxxxxroutetable1 op monitor interval=20s timeout=40s --group grp_RHX_ERS10

Notes for ASCS and ERS

  • If more than one route table is required for connectivity or because of subnet associations, the routing_table parameter can have multiple values separated by a comma. For example, routing_table=rtb-xxxxxroutetable1, rtb-xxxxxroutetable2.

  • Additional parameters – lookup_type and routing_table_role are required for shared VPC. For more information, see Shared VPC – optional.

Create SAPInstance resources

The SAP instance is started and stopped using cluster resources. Modify and run the commands in the table to create SAPInstance resources.

Note

The change between ENSA1 and ENSA2 that allows the lock table to be consumed remotely, means that for ENSA2, ASCS can restart in its current location (assuming the node is still available). This change impacts stickiness, migration, and priority parameters. Ensure to use the right command for your enqueue version.

ENSA1

Use the following command to create an ASCS SAPInstance resource.

pcs resource create rsc_sap_RHX_ASCS00 ocf:heartbeat:SAPInstance InstanceName="RHX_ASCS00_rhxascs" START_PROFILE=/usr/sap/RHX/SYS/profile/RHX_ASCS00_rhxascs AUTOMATIC_RECOVER=false meta resource-stickiness=5000 migration-threshold=1 op monitor interval=20s on-fail=restart timeout=60s op start interval=0s timeout=240s op stop interval=0s timeout=600s --group grp_RHX_ASCS00

Add a resource stickiness to the group to ensure that ASCS will stay on node, if possible.

pcs resource meta grp_RHX_ASCS00 resource-stickiness=3000

Use the following command to create an ERS SAPInstance resource.

pcs resource create rsc_sap_RHX_ERS10 ocf:heartbeat:SAPInstance InstanceName="RHX_ERS10_rhxers" START_PROFILE=/usr/sap/RHX/SYS/profile/RHX_ERS10_rhxers AUTOMATIC_RECOVER=false IS_ERS=true op monitor interval=20s on-fail=restart timeout=60s op start interval=0s timeout=600s op stop interval=0s timeout=240s --group grp_RHX_ERS10
ENSA2

Use the following command to create an ASCS SAPInstance resource.

pcs resource create rsc_sap_RHX_ASCS00 ocf:heartbeat:SAPInstance InstanceName="RHX_ASCS00_rhxascs" START_PROFILE=/usr/sap/RHX/SYS/profile/RHX_ASCS00_rhxascs AUTOMATIC_RECOVER=false meta resource-stickiness=5000 op monitor interval=11s on-fail=restart timeout=60s op start interval=0s timeout=600s op stop interval=0s timeout=240s --group grp_RHX_ASCS00

Add a resource stickiness to the group to ensure that ASCS will stay on node, if possible.

pcs resource meta grp_RHX_ASCS00 resource-stickiness=3000
Note

meta resource-stickiness=5000is here to balance the failover constraint with ERS, so the resource stays on the node where it started, and doesn't migrate around cluster uncontrollably.

Use the following command to create an ERS SAPInstance resource.

pcs resource create rsc_sap_RHX_ERS10 ocf:heartbeat:SAPInstance InstanceName="RHX_ERS10_rhxers" START_PROFILE=/usr/sap/RHX/SYS/profile/RHX_ERS10_rhxers AUTOMATIC_RECOVER=false op monitor interval=20s on-fail=restart timeout=60s op start interval=0s timeout=600s op stop interval=0s timeout=240s --group grp_RHX_ERS10

The difference between ENSA1 and ENSA2 is that ENSA2 allows the lock table to be consumed remotely, which means that for ENSA2, ASCS can restart in its current location (assuming the node is still available). This change impacts stickiness, migration and priority parameters. Ensure that you use the right command for your enqueue version.

Create resource constraints

Resource constraints are used to determine where resources run, or alternatively where resources are located, per the conditions. Constraints for SAP NetWeaver ensure that ASCS and ERS are started on separate nodes, and locks are preserved in case of failures. The following are the different types of constraints.

Colocation constraint

The negative score ensures that ASCS and ERS are run on separate nodes, wherever possible.

pcs constraint colocation add grp_RHX_ERS10 with grp_RHX_ASCS00 -5000

Order constraint

This constraint ensures the ASCS instance is started prior to stopping the ERS instance. This can be necessary to consume the lock table.

pcs constraint order start grp_RHX_ASCS00 then stop grp_RHX_ERS10 symmetrical=false kind=Optional

Location constraint (ENSA1 only)

This constraint is only required for ENSA1. The lock table can be retrieved remotely for ENSA2, and as a result ASCS doesn't failover to where ERS is running.

pcs constraint location rsc_sap_RHX_ASCS00 rule score=2000 runs_ers_RHX eq 1

Activate cluster

Use pcs config show to review that all the values have been entered correctly.

On confirmation of correct values, set the maintenance mode to false using the following command. This enables the cluster to take control of the resources.

pcs property set maintenance-mode=false

See the Sample configuration.