SAP S/4HANA - Enqueue Replication 2 High Availability Cluster With Simple Mount #

The following sections focus on background information and the purpose of the document at hand.

The document at hand explains how to:

This guide focuses on high availability of the central services. For high availabiliy of the SAP HANA database, consult the guide for the scale-up performance-optimized scenario (see Section 1.2, “Additional documentation and resources”).

This document describes setting up a pacemaker cluster using SUSE Linux Enterprise Server for SAP applications 16 for the Enqueue Replication scenario. For the setup described in this document, two or three nodes are used for the ASCS central services instance and ERS replicated enqueue instance. These nodes are controlled by the SUSE Linux Enterprise High Availability cluster. Additional nodes are used for running the database, and the PAS and AAS application server instances. Finally, you need a highly available NFS server.

The goals for the setup include:

All shared SAP resources are located on a central NFS server.

Shared disks allow using SBD as the cluster fencing mechanism.

3.1 Installing a typical systems for ASCS, ERS, database and additional SAP instances #

 

The document at hand describes the installation of a distributed SAP system on three and more systems. In this setup, only two or three systems reside inside the cluster. The database and SAP dialog instances can be controlled by another cluster. We recommend installing the database on a separate cluster. The cluster configuration for three and more nodes is described at the end of this document. The number of nodes within one cluster should be either two or an odd number.

Note

The cluster described in this guide manages only the SAP central services instances ASCS and ERS.

For the SAP HANA database, we recommend setting up the performance-optimized system replication scenario with SAPHanaSR-angi. The SAPHanaSR-angi solution should be set up in a separate two-node cluster. The setup is described in a separate best practices document available from the SUSE Best Practices on documentation portal at https://documentation.suse.com/sbp/sap-16/.

Figure 1: Typical systems #

 

Clustered machines Two-Node scenario #

 

• One machine (valuga11) for ASCS; Virtual hostname: sapen2as

• One machine (valuga12) for ERS; Virtual hostname: sapen2er

Also needed machines - optionally clustered #

 

• One machine (valuga01) for DB; Virtual hostname: sapen2db

• One machine (valuga13) for the PAS; Virtual hostname: sapen2d1

• One machine (valuga14) for the AAS; Virtual hostname: sapen2d2

3.2 Implementing high avaiability for the SAP HANA databse - optional #

 

We recommend implementing SAP HANA system replication (SR) automation to enhance the scenario described in this document.

Figure 2: One cluster for central services, one for SAP HANA SR #

 

Use the version for SAP S/4HANA ABAP Platform on Linux on AMD64/Intel 64 and IBM PowerLE. Find more information about the supported combinations of OS and databases for SAP S/4HANA Server 2021 or newer at the SAP Product Availability Matrix at SAP PAM.

3.3 Integrating SAP S/4HANA into the cluster using the Cluster Connector #

 

The integration of the HA cluster through the SAP control framework using the sap_suse_cluster_connector is of special interest. The service sapstartsrv controls SAP instances starting with SAP Kernel versions 6.40. One of the classic problems running SAP instances in a highly available environment is the following: If an SAP administrator changes the status (start/stop) of an SAP instance without using the cluster software interfaces, the cluster framework detects that as an error status. The framework then restores the SAP instance to its previous status by either starting or stopping it. This can result in very dangerous situations, if the cluster changes the status of an SAP instance during some SAP maintenance tasks. The new updated solution enables the central component sapstartsrv to report status changes to the cluster software. This avoids dangerous situations as previously described. For more details, read the blog article "Using sap_vendor_cluster_connector for interaction between cluster framework and sapstartsrv" at https://blogs.sap.com/2014/05/08/using-sapvendorclusterconnector-for-interaction-between-cluster-framework-and-sapstartsrv/comment-page-1/.

Figure 3: Cluster connector to integrate the cluster with the SAP start framework #

 

For this scenario, the latest version of the sap-suse-cluster-connector is used. It implements the API version 3 for the communication between the cluster framework and the sapstartsrv service.

The latest version of the sap-suse-cluster-connector allows starting, stopping and migrating an SAP instance. The integration between the cluster software and the sapstartsrv also implements the option to run checks of the HA setup using either the command line tool sapcontrol or the SAP management consoles (SAP MMC or SAP MC). Starting with version 3.1.0, the maintenance mode of cluster resources triggered with SAP sapcontrol commands is supported. See also manual page sap_suse_cluster_connector(8).

3.4 Sharing disks and NFS #

 

XFS is used for all local file systems. For /sapmnt/<SID> and /usr/sap/<SID>, NFS is used.

3.4.1 Sharing disk for SBD and mounting NFS for cluster ASCS and ERS #

 

The disk for the fencing mechanism SBD must be shared and assigned to the cluster nodes valuga11 and valuga12 in the two-node cluster example. The NFS file systems for the ASCS and ERS instances are mounted both on valuga11 and valuga12. They can also be mounted on the SAP application servers (in this example valuga13/PAS and valuga14/AAS) to simplify the storage layout of the complete SAP system.

Make sure that your shared SBD disk /dev/disk/by-id/SUSE-Example-A is visible on valuga11 and valuga12:

# lsblk | grep /dev/disk/by-id/SUSE-Example-A

During the SAP software installation, you need to mount via NFS and entries in /etc/fstab.

3.4.2 Preparing the disk for database and dialog instances (HANA DB) #

 

The disk /dev/disk/by-id/SUSE-Example-B for the database (260 GB) is assigned to valuga01 and formatted with XFS.

You can either use YaST or available command line tools to create the partitions. The following script can be used for non-interactive setups.

Example 1: Create Partitions and File Systems for DB and App Servers on valuga01 #

 

# lsblk
# parted -s /dev/disk/by-id/SUSE-Example-B print
# # we are on the 'correct' drive, right?
# mkfs.xfs /dev/disk/by-id/SUSE-Example-B
# mkdir /hana
# echo "/dev/disk/by-id/SUSE-Example-B /hana xfs defaults 0 2" >> /etc/fstab
# mount /dev/disk/by-id/SUSE-Example-B

Note

D01: Starting with NetWeaver 7.5, the primary application server instance directory is named 'D<Instance_Number>'.

NFS server #

 

• 192.168.1.1:/data/export/S4_HA_CLU_10/EN2/sapmnt/EN2 /sapmnt/EN2

• 192.168.1.1:/data/export/S4_HA_CLU_10/EN2/usr/sap/EN2 /usr/sap/EN2

Media #

 

• 192.168.1.1:/sapmedia /sapmedia

192.168.1.100  valuga01
192.168.1.103  valuga11
192.168.1.104  valuga12
192.168.1.105  valuga13

192.168.1.112  sapen2as
192.168.1.113  sapen2er
192.168.1.114  sapen2db
192.168.1.110  sapen2d1
192.168.1.111  sapen2d2

# mkdir -p /sapmnt/EN2 /usr/sap/EN2 /sapmedia
# echo "192.168.1.1:/data/export/S4_HA_CLU_10/EN2/sapmnt/EN2 /sapmnt/EN2 nfs defaults 0 0" >> /etc/fstab
# echo "192.168.1.1:/data/export/S4_HA_CLU_10/EN2/usr/sap/EN2 /usr/sap/EN2 nfs defaults 0 0" >> /etc/fstab
# mount /sapmnt/EN2
# mount /usr/sap/EN2

The overall procedure to install the distributed SAP system is as follows:

The result is a distributed SAP installation as illustrated here:

Figure 4: Distributed installation of the SAP system #

 

Group sapinst      1001
Group sapsys       1002
Group ha1shm       1003

User  en2adm       2001
User  sapadm       2002
User  ha1adm       2003

# ip a a 192.168.1.112/24 dev ens1
# # if not mounted yet, mount these now
# mount /sapmnt/EN2
# mount /usr/sap/EN2
# cd /sapmedia/SWPM20_P9/
# ./sapinst SAPINST_USE_HOSTNAME=sapen2as

# chown -R en2adm:sapsys /usr/sap/EN2/ASCS00

# ip a a 192.168.1.113/24 dev ens1
# # if not mounted yet, mount these now
# mount /sapmnt/EN2
# mount /usr/sap/EN2
# cd /sapmedia/SWPM20_P9/
# ./sapinst SAPINST_USE_HOSTNAME=sapen2er

# chown -R en2adm:sapsys /usr/sap/EN2/ERS10

# sapcontrol -nr 00 -function Stop    # to stop the ASCS
# sapcontrol -nr 00 -function Start   # to start the ASCS

4.4 Performing subsequent steps for ASCS and ERS #

 

After installation, you can perform several subsequent steps on the ASCS and ERS instances.

4.4.1 Stopping ASCS and ERS #

 

To stop the ASCS and ERS instances, use the commands below. On valuga11, do the following:

# su - en2adm
# sapcontrol -nr 00 -function Stop
# sapcontrol -nr 00 -function StopService

On valuga12, do the following:

# su - en2adm
# sapcontrol -nr 10 -function Stop
# sapcontrol -nr 10 -function StopService

4.4.2 Register ASCS and ERS #

 

ASCS is installed on the first cluster node, ERS is installed on the second. To integrate ASCS and ERS with systemd on all cluster nodes, the SAP instances need to be registered on each node.

On the first cluster node ERS needs to be registred, on the second cluster node ASCS needs to be registered.

• Register the ERS SAP instance on the first cluster node (valuga11):

  # LD_LIBRARY_PATH=/usr/sap/hostctrl/exe:$LD_LIBRARY_PATH; export LD_LIBRARY_PATH
  # /usr/sap/hostctrl/exe/sapstartsrv pf=/usr/sap/<SID>/SYS/profile/<SID>_ERS<instanceNumberErs>_<virtHostNameErs> -reg

• Register the ASCS SAP instance on the second cluster node (valuga12):

  # LD_LIBRARY_PATH=/usr/sap/hostctrl/exe:$LD_LIBRARY_PATH; export LD_LIBRARY_PATH
  # /usr/sap/hostctrl/exe/sapstartsrv pf=/usr/sap/<SID>/SYS/profile/<SID>_ASCS<instanceNumberAscs>_<virtHostNameAscs> -reg

After registration, the list of systemd services must be the same and should like:

# systemctl list-unit-files | grep SAP
SAPEN2_00.service disabled disabled
SAPEN2_10.service disabled disabled
SAP.slice  static -

After registration, the service might still be enabled. The next section describes how to disable the SAP<sid>_<ino> services.

4.4.3 Disabling systemd services of the ASCS and the ERS SAP instance #

 

This step is required to transfer control of the instance to the high-availability (HA) cluster. See also manual pages ocf_suse_SAPStartSrv(7) and SAPStartSrv_basic_Cluster(7).

# systemctl disable SAPEN2_00.service
# systemctl stop SAPEN2_00.service
# systemctl disable SAPEN2_10.service
# systemctl stop SAPEN2_10.service

Note

Stopping the instance services will stop the SAP instance as well. Starting the instance services will not start the SAP instances.

• Check the SAP systemd integration:

# systemctl list-unit-files | grep SAP
SAPEN2_00.service disabled disabled
SAPEN2_10.service disabled disabled

The instance services are indeed disabled, as required.

# systemctl list-unit-files | grep sap
saphostagent.service enabled
sapinit.service generated
saprouter.service disabled
saptune.service enabled

The mandatory saphostagent service is enabled. This is the installation default. Some more SAP related services might be enabled, for example the recommended saptune.

# cat /usr/sap/sapservices
systemctl --no-ask-password start SAPEN2_00 # sapstartsrv pf=/usr/sap/EN2/SYS/profile/EN2_ASCS00_sapen2as
systemctl --no-ask-password start SAPEN2_10 # sapstartsrv pf=/usr/sap/EN2/SYS/profile/EN2_ERS10_sapen2er

The sapservices file remains for compatibility. It lists native systemd commands, with one line per registered instance.

4.4.4 Integrating the cluster framework using sap-suse-cluster-connector #

 

For the ERS and ASCS instances, edit the instance profiles EN2_ASCS00_sapen2as and EN2_ERS10_sapen2er in the profile directory /usr/sap/EN2/SYS/profile/.

Configure the sapstartsrv service to load the HA script connector library and use the connector sap-suse-cluster-connector. Ensure the feature Autostart is not used.

service/halib = $(DIR_EXECUTABLE)/saphascriptco.so
service/halib_cluster_connector = /usr/bin/sap_suse_cluster_connector

Add the user en2adm to the Unix user group haclient.

# usermod -a -G haclient en2adm

See also manual pages sap_suse_cluster_connector(8), usermod(8) and groupmod(8).

4.4.5 Adapting SAP profiles #

 

For the ASCS instance, change the start command from Restart_Program_xx to Start_Program_xx for the enqueue server (Enqueue Server 2). This setting prevents the SAP start framework from automatically restarting the enqueue process. A restart results in lost locks..

File /usr/sap/EN2/SYS/profile/EN2_ASCS00_sapen2as:

Start_Program_01 = local $(_ENQ) pf=$(_PF)

Optionally, you can limit the number of restarts of services (in the case of ASCS, this limits the restart of the message server).

For the ERS instance, change the start command from Restart_Program_xx to Start_Program_xx for the enqueue replication server (Enqueue Replicator 2).

File /usr/sap/EN2/SYS/profile/EN2_ERS10_sapen2er:

Start_Program_00 = local $(_ENQR) pf=$(_PF) NR=$(SCSID)

4.4.6 Starting ASCS and ERS #

 

To start the ASCS and ERS instances, use the commands below.

On valuga12, type the following

# su - en2adm
# sapcontrol -nr 10 -function StartService EN2
# sapcontrol -nr 10 -function Start

On valuga11, type the following:

# su - en2adm
# sapcontrol -nr 00 -function StartService EN2
# sapcontrol -nr 00 -function Start

# ip a a 192.168.1.114/24 dev ens1
# mount /dev/disk/by-id/SUSE-Example-B /hana
# cd /sapmedia/SWPM20_P9/
# ./sapinst SAPINST_USE_HOSTNAME=sapen2db

# ip a a 192.168.1.110/24 dev ens1
# mount /dev/disk/by-id/SUSE-Example-B-part2 /usr/sap/EN2/D01
# cd /sapmedia/SWPM20_P9/
# ./sapinst SAPINST_USE_HOSTNAME=sapen2d1

# ip a a 192.168.1.111/24 dev ens1
# mount /dev/disk/by-id/SUSE-Example-B-part3 /usr/sap/EN2/D02
# cd /sapmedia/SWPM20_P9/
# ./sapinst SAPINST_USE_HOSTNAME=sapen2d2

# cd /sapmedia/SWPM20_P9/
# ./sapinst

The main procedure to implement the cluster is as follows:

Note

Before you continue to set up the cluster, perform the following actions: First, stop all SAP instances. Then, remove the (manually added) IP addresses on the cluster nodes. Finally, unmount the file systems which will be controlled by the cluster later.

Note

Create the SBD device/partition before starting. Verify which device/partition to use. In this setup guide, the disk /dev/disk/by-id/SUSE-Example-A is reserved for SBD usage.

# modprobe softdog
# echo softdog > /etc/modules-load.d/watchdog.conf
# systemctl restart systemd-modules-load
# lsmod | egrep "(wd|dog|i6|iT|ibm)"

# crm cluster init -s  /dev/disk/by-id/SUSE-Example-A

# modprobe softdog
# echo softdog > /etc/modules-load.d/watchdog.conf
# systemctl restart systemd-modules-load
# lsmod | egrep "(wd|dog|i6|iT|ibm)"

# crm cluster join -c valuga11

Stack: corosync
Current DC: valuga11 (version 1.1.18+20180430.b12c320f5-1.14-b12c320f5) - partition with quorum
Last updated: Mon Jan 28 13:10:37 2019
Last change: Wed Jan 23 09:52:57 2019 by root via cibadmin on valuga11

2 nodes configured
1 resource configured

Online: [ valuga11 valuga12 ]

fencing-sbd	(stonith:fence_sbd):	Started valuga11

5.3 Configuring cluster resources #

 

The SAPInstance resource configuration is needed to start and stop the ASCS and the ERS instances themselves. See manual page ocf_heartbeat_SAPInstance(7) for details.

The SAPStartSrv resource starts and stops the sapstartsrv service and guarantees that only one instance is running per cluster at the same time. See manual page ocf_suse_SAPStartSrv(7) for details.

In the latest version of ENSA2, the ASCS instance receives the enqueue lock table over the network from the ERS instance. Usually, both instances run on different nodes. However, if only node is available, the ASCS instance starts on the same host as the the ERS instance.

Figure 5: Resources and constraints #

 

5.3.1 Preparing the cluster for adding the resources #

 

To prevent the cluster from starting partially defined resources, set the cluster to maintenance mode. This deactivates all monitor actions.

As user root, type the following command:

# crm configure property maintenance-mode=true

5.3.2 Preparing the new SAPStartSrv resource agent implementation #

 

As a prerequisite for having a single NFS mount for ASCS and ERS, the sapstartsrv instance agents of ASCS and ERS must not be started by the sapinit service during system start-up, as these services are started and stopped by dedicated cluster resources.

With the sapstartsrv-resource-agents RPM package, two systemd services called sapping and sappong are included. sapping runs before sapinit and moves /usr/sap/sapservices out of the way. Consequently, the sapstartsrv instance agents are not started automatically by sapinit. sappong runs after sapinit and moves /usr/sap/sapservices back to its original location.

On valuga11 and valuga12, enable the sapping and sappong services.

# systemctl enable sapping
# systemctl enable sappong

See manual pages ocf_suse_SAPStartSrv(7), sapping(8) and SAPStartSrv_basic_cluster(7) for details.

5.3.3 Configuring resources for the ASCS Instance #

 

First, configure the resources for the IP address, the SAP instance agent and the SAP instance. You need to adapt the parameters for your specific environment.

Ensure the parameter MINIMAL_PROBE is set to true in the SAP instance definition .

Example 3: ASCS primitive #

 

primitive rsc_ip_EN2_ASCS00 IPaddr2 \
  params ip=192.168.1.112 \
  op monitor interval=21 timeout=20
primitive rsc_SAPStartSrv_EN2_ASCS00 ocf:suse:SAPStartSrv \
  params InstanceName=EN2_ASCS00_sapen2as
primitive rsc_sap_EN2_ASCS00 SAPInstance \
  op monitor interval=22 timeout=60 on-fail=restart \
  params InstanceName=EN2_ASCS00_sapen2as \
     START_PROFILE="/usr/sap/EN2/SYS/profile/EN2_ASCS00_sapen2as" \
     AUTOMATIC_RECOVER=false MINIMAL_PROBE=true \
  meta resource-stickiness=5000

The shown SAPInstance monitor timeout is a trade-off between fast recovery of the ASCS vs. resilience against sporadic temporary NFS issues. You may slightly increase it to fit your infrastructure. Consult the storage or NFS server documentation for appropriate timeout values. Make sure the SAPStartSrv resource has NO monitor operation configured. See also manual pages ocf_heartbeat_SAPInstance(7), ocf_heartbeat_IPaddr2(7), ocf_suse_SAPStartSrv(7) and nfs(5).

Example 4: ASCS group #

 

group grp_EN2_ASCS00 \
  rsc_ip_EN2_ASCS00 rsc_SAPStartSrv_EN2_ASCS00 rsc_sap_EN2_ASCS00 \
  meta resource-stickiness=3000

Create a txt file (like crm_ascs.txt) with your preferred text editor. Add both examples (primitives and group) to that file and load the configuration to the cluster manager configuration.

As user root, type the following command:

# crm configure load update crm_ascs.txt

5.3.4 Configuring resources for the ERS Instance #

 

Next, configure the resources for the IP address, the SAP instance agent and the SAP instance. You need to adapt the parameters for your specific environment.

Ensure the parameter MINIMAL_PROBE is set to true in the SAP instance definition .

The specific parameter IS_ERS=true must only be set for the ERS instance.

Example 5: ERS primitive #

 

primitive rsc_ip_EN2_ERS10 IPaddr2 \
  params ip=192.168.1.113 \
  op monitor interval=10 timeout=20
primitive rsc_SAPStartSrv_EN2_ERS10 ocf:suse:SAPStartSrv \
  params InstanceName=EN2_ERS10_sapen2er
primitive rsc_sap_EN2_ERS10 SAPInstance \
  op monitor interval=22 timeout=60 on-fail=restart \
  params InstanceName=EN2_ERS10_sapen2er \
     START_PROFILE="/usr/sap/EN2/SYS/profile/EN2_ERS10_sapen2er" \
     AUTOMATIC_RECOVER=false IS_ERS=true MINIMAL_PROBE=true

The shown SAPInstance monitor timeout is a trade-off between fast recovery of the ERS vs. resilience against sporadic temporary NFS issues. You may slightly increase it to fit your infrastructure. Consult the storage or NFS server documentation for appropriate timeout values. Essure the SAPStartSrv resource has NO monitor operation configured. See also manual pages ocf_heartbeat_SAPInstance(7), ocf_heartbeat_IPaddr2(7) ocf_suse_SAPStartSrv(7) and nfs(5).

Example 6: ERS group #

 

group grp_EN2_ERS10 \
  rsc_ip_EN2_ERS10 rsc_SAPStartSrv_EN2_ERS10 rsc_sap_EN2_ERS10

Create a txt file (like crm_ers.txt) with your preferred text editor. Add both examples (primitives and group) to that file and load the configuration to the cluster manager configuration.

As user root, type the following command:

# crm configure load update crm_ers.txt

5.3.5 Configuring the colocation constraints between ASCS and ERS #

 

An ASCS instance should avoid starting up on the cluster node running the ERS instance if any other node is available. The ENSA2 setup can resynchronize the lock table over the network.

If the ASCS instance has been started by the cluster on the ERS node, the ERS instance should be moved to another cluster node (col_sap_EN2_no_both). This constraint is needed to ensure that the ERS instance will synchronize the locks again and the cluster is ready for an additional takeover.

Example 7: Location constraint #

 

colocation col_sap_EN2_separate -5000: grp_EN2_ERS10 grp_EN2_ASCS00
order ord_sap_EN2_ascs_first Optional: rsc_sap_EN2_ASCS00:start \
      rsc_sap_EN2_ERS10:stop symmetrical=false

Create a txt file (like crm_col.txt) with a text editor. Add both constraints to that file and load the configuration to the cluster manager configuration.

As user root, type the following command:

# crm configure load update crm_col.txt

5.3.6 Activating the cluster #

 

The last step is to end the cluster maintenance mode and allow the cluster to detect already running resources.

As user root, type the following command:

# crm configure property maintenance-mode="false"

Multi-node cluster setups are cluster configurations with more than two nodes. Depending on the starting point, you can or extend a two-node cluster setup or directly start with more than two nodes for an ASCS / ERS high availability setup. The following examples show how to set up a multi-node cluster and how to extend an existing two-node cluster. They outline major configuration changes and the basic preparation of a new member node. The task list for setting up a three-node cluster is similar to the task list for a two-node cluster. However, some details differ to allow for a diskless SBD setup. A diskless SBD setup is an optional improvement for three nodes, but does not work on two nodes. Conversely, priority fencing is an optional improvement for two nodes, but does not work on three nodes. An example priority fencing configuration for a two-node cluster is available in the appendix. See the SUSE Linux Enterprise High Availability product documentation for details.

Note

When extending a cluster from two to three nodes, make sure to not use priority fencing.

6.1 Extending an existing two-node cluster configuration #

 

Tasks #

 

1. Backing up the current cluster

2. Installing the operating system of the new node

3. Patching the existing nodes

4. Preparing the new node’s operating system

5. Installing the cluster software on the new node

6. Preparing SAPStartSrv resource agent on the new node

7. Preparing the SAP installation on the new node

8. Adding the new node to the cluster

9. Testing the new cluster configuration

6.1.1 Backing up the current cluster #

 

To back up the current cluster, perform a

• Backup of your system including

  • cluster configuration

  • corosync.conf

  • all data and configuration which are important and customized and not default

The system is configured as described in the SUSE Best Practices document SAP S/4 HANA - Enqueue Replication 2 High Availability Cluster With Simple Mount - Setup Guide.

To back up the cluster configuration, go to one of the cluster nodes and save the cluster configuration with the crm and crm report commands:

# crm configure save 2nodes_crm.txt
# supportconfig

Back up the existing /etc/corosync/corosync.conf and all other files required to restore the system. The following example is one method for creating a backup. The important step is storing the backup on an external destination.

# tar cvf /<path to external storage>/backup_2nodes_configuration.tar \
    /etc/corosync/corosync.conf \
    /etc/corosync/authkey \
    /etc/sysconfig/sbd \
    2nodes_crm.txt \
    /var/log/scc_*txz
    <add your additional files here>

6.1.2 Installing the operating system of the new node #

 

We recommend using automated installation to ensure that the system setup across nodes is identical. Document any additional steps taken beyond the automated setup. In this example, we deploy machines with Agama and use Ansible for configuration.

6.1.3 Patching the existing nodes #

 

If applicable, install the latest updates and patches on your existing nodes. Alternatively, if you are using frozen repositories, such as those provided by SUSE Multi Linux Manager, add the new system to the same repositories to ensure they have the same patch level as your existing nodes.

Use zypper patch or zypper update, depending on your company’s rules.

• We recommend installing the latest available patches to guarantee system stability and hardening. Bug fixing and security patches help avoid unplanned outages and make the system less vulnerable.

There are multiple ways to do so:

# zypper patch
## or
# zypper update

6.1.4 Preparing the new node’s operating system #

 

Example 8: Check for valid DNS, time synchronization, network settings #

 

• Verify that DNS is working:

  # ping <hostname>

• Set up chrony (this is best done with yast2) and enable it:

  # yast ntp-client

• Check the network settings:

  # ip r

You may run into trouble if there is no valid or no default route configured.

• Patch the new system like the existing nodes, verify that your systems have the same patch level and that all required reboots have been performed.

6.1.5 Installing cluster software on the new node #

 

Example 9: Installing packages #

 

• Install the pattern sles_sap_HAAPP on the new cluster node:

  # zypper in -t pattern sles_sap_HAAPP

6.1.6 Preparing SAPStartSrv resource agent on the new node #

 

• Enable the sapping and sappong services.

  # systemctl enable sapping
  # systemctl enable sappong

After installing all necessary packages, compare the installed package versions.

Example 10: Check if all nodes have the same software packages and versions: #

 

• On the existing cluster nodes, type:

  # rpm -qa | sort >rpm_valuga11.txt

• On the new node, type:

  # rpm -qa | sort >rpm_valuga13.txt

• Copy the file from one node to the other and compare the two versions:

  # vimdiff rpm_valuga13.txt rpm_valuga11.txt

Note

If there are any differences, fix them first before you proceed.

Example 11: Install and configure the watchdog device on the new machine. #

 

Instead of deploying the software-based solution, use a hardware-based watchdog device. The following example uses the software device but can be easily adapted to the hardware device.

# modprobe softdog
# echo softdog > /etc/modules-load.d/watchdog.conf
# systemctl restart systemd-modules-load
# lsmod | egrep "(wd|dog|i6|iT|ibm)"

Note

Ensure that the new node is connected to the same SBD disk connected to the existing two nodes. Ensure that the new node has identic SBD configurations as the two existing nodes

# sbd -d /dev/disk/by-id/SUSE-Example-A dump

6.1.7 Preparing the SAP installation on the new node #

 

With SWPM 2.0 (SP4 or later), which is part of the SL Toolset, SAP provides a new option which can perform all necessary steps to prepare a fresh install server to be able to fit into an existing SAP system. This new option helps to prepare a new host which can later run either ASCS or ERS in the cluster environment.

Create the directory structure that should run the SAP resource. The instance directory is located on an NFS share for all nodes.

• Create mount points and mount NFS shares on the new added node (valuga13):

Example 12: Mount NFS Shares on valuga13 #

 

# mkdir -p /sapmnt/EN2 /usr/sap/EN2 /sapmedia
# mount -t nfs 192.168.1.1:/data/export/S4_HA_CLU_10/EN2/sapmnt/EN2    /sapmnt/EN2
# mount -t nfs 192.168.1.1:/data/export/S4_HA_CLU_10/EN2/usr/sap/EN2    /usr/sap/EN2
# mount -t nfs 192.168.1.1:/sapmedia /sapmedia

As the directories /sapmnt/EN2, /usr/sap/EN2 need to be available at all time, make sure they are mounted during boot. This can be achieved by putting the information into the /etc/fstab.

The next step requires the following information:

• profile directory

• password for SAP System Administrator

• UID for sapadm

# cd /sapmedia/SWPM20_P9/
# ./sapinst

• SWPM product installation path:

  • Installing SAP S/4HANA Server 2021 → SAP HANA DATABASE → Installation → Application Server ABAP → High-Availability System → Prepare Additional Cluster Node

• Use /sapmnt/EN2/profile for the profile directory

• All passwords: <use-your-secure-pwd>

• UID for sapadm: 2002

Example 13: Post Step Procedure after SAP Preparation Step #

 

• Add the user en2adm to the Unix user group haclient.

  # usermod -a -G haclient en2adm

• Register the ASCS and the ERS SAP instance:

  # LD_LIBRARY_PATH=/usr/sap/hostctrl/exe:$LD_LIBRARY_PATH; export LD_LIBRARY_PATH
  # /usr/sap/hostctrl/exe/sapstartsrv pf=/usr/sap/<SID>/SYS/profile/<SID>_ERS<instanceNumberErs>_<virtHostNameErs> -reg
  # /usr/sap/hostctrl/exe/sapstartsrv pf=/usr/sap/<SID>/SYS/profile/<SID>_ASCS<instanceNumberAscs>_<virtHostNameAscs> -reg

  

  Note

  This must be done for each instance. Call sapstartsrv with parameters pf=<profile-of-the-sap-instance> and -reg.

• Disable systemd services of the ASCS and the ERS SAP instance:

  # systemctl disable SAPEN2_00.service
  # systemctl disable SAPEN2_10.service

  

  Note

  This is mandatory for giving control over the instance to the HA cluster.

• Check the SAP systemd integration:

  # systemctl list-unit-files | grep sap
  saphostagent.service enabled
  sapinit.service generated
  saprouter.service disabled
  saptune.service enabled
  # systemctl list-unit-files | grep SAP
  SAPEN2_10.service disabled
  SAPEN2_10.service disabled
  # cat /usr/sap/sapservices
  systemctl --no-ask-password start SAPEN2_00 # sapstartsrv pf=/usr/sap/EN2/SYS/profile/EN2_ASCS00_sapen2as
  systemctl --no-ask-password start SAPEN2_10 # sapstartsrv pf=/usr/sap/EN2/SYS/profile/EN2_ERS10_sapen2er

6.1.8 Adding the new node to the cluster #

 

Example 14: Adding the New Node to the Cluster #

 

Check if the SBD device is available in case the SBD fencing method is in place for the two nodes. If the existing cluster uses a different, supported fencing mechanism, check and verify it also for the new cluster node.

# sbd -d /dev/disk/by-id/SUSE-Example-A dump

• Joining the cluster can be done with crm cluster join:

# crm cluster join -c valuga11

After the new node has joined the cluster, the configuration must be adapted to the new situation. Double-check if joining the cluster was successful and verify the file /etc/corosync/corosync.conf.

# awk '/quorum/,/}/' /etc/corosync/corosync.conf
# corosync-quorumtool -s

The values expected_votes and two_node should now look like the following on all nodes:

expected_votes: 3
two_node: 0

Modify the cluster configuration and set a new colocation rule with crm:

# crm configure delete col_sap_EN2_no_both
# crm configure colocation ASCS00_ERS10_separated_EN2 -5000: grp_EN2_ERS10 grp_EN2_ASCS00

6.1.9 Testing the new cluster configuration #

 

We recommend running test to verify that the new configuration is working as expected. Find a list of tests in the basic setup for the two node cluster above.

For more information, see the documents listed below.

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