Chapter 7. Adding a node to the cluster

Procedure

1. On the new node, go to the directory where you have extracted the installation media:

   [root]# cd <software_path>

   • Replace <software_path> with the path to your unpacked media, for example, /sapmedia/SWPM20_SP19/.

2. Run the installer command on the new node:

   [root]# ./sapinst

3. Open the web installer UI using the link provided in the terminal.
4. Open the SAP product you want to install and enter the installation option. Expand the High-Availability System option and select Prepare Additional Cluster Node. Click Next.

5. Provide the requested installation information on each page and click Next to move forward.

   Some steps, like extracting SAP packages, can take a while. Keep an eye on the terminal in which you started the installer for details of the ongoing process that are not displayed in the web UI.

Verification

1. Check that the new node has the SAP ports in the services file. For example, count the entries that contain SAP System in their port description and compare the result on all existing nodes:

   [root]# grep -i "SAP System" /etc/services | wc -l
   401

   Update the /etc/services file on the node if it is missing entries.

2. Check that the /usr/sap/hostctrl/ path is present and that the version is the same as on the existing cluster nodes:

   [root]# /usr/sap/hostctrl/exe/saphostexec -version

Verification

1. Check that the file exists and has the same owner and permissions as on the source node:

   [root]# ls -lh /usr/sap/sapservices
   -rwxr-xr-x. 1 root sapinst 208 Jun 16 13:59 /usr/sap/sapservices

2. Check that the file contains the configured instances, for example, ASCS and ERS:

   [root]# cat /usr/sap/sapservices
   systemctl --no-ask-password start SAPS4H_20 # sapstartsrv pf=/usr/sap/S4H/SYS/profile/S4H_ASCS20_s4hascs
   systemctl --no-ask-password start SAPS4H_29 # sapstartsrv pf=/usr/sap/S4H/SYS/profile/S4H_ERS29_s4hers

Procedure

1. Register the ASCS instance. Run the following SAP command as the root user on the new node to create the systemd integration:

   [root]# export LD_LIBRARY_PATH=/usr/sap/<SID>/ASCS<instance>/exe && \
   /usr/sap/<SID>/ASCS<instance>/exe/sapstartsrv \
   pf=/usr/sap/<SID>/SYS/profile/<SID>_ASCS<instance>_<ascs_virtual_hostname> \
   -reg

   The command executes the sapstartsrv service for the selected instance profile and registers the instance service on the current system. It creates the systemd unit for the instance service, if it does not exist, and updates the local /usr/sap/sapservices file.

   • Replace <SID> with your ASCS instance SID, for example, S4H.
   • Replace <instance> with your ASCS instance number, for example, 20.
   • Replace <ascs_virtual_hostname> with the virtual hostname for your ASCS instance, for example, s4hascs.

2. Register the ERS instance by repeating step 1 for the ERS profile:

   [root]# export LD_LIBRARY_PATH=/usr/sap/<SID>/ERS<instance>/exe && \
   /usr/sap/<SID>/ERS<instance>/exe/sapstartsrv \
   pf=/usr/sap/<SID>/SYS/profile/<SID>_ERS<instance>_<ers_virtual_hostname> \
   -reg

3. Optional: Register any PAS or AAS instance by repeating step 1 for the respective application server profile. Skip this step if you have not configured PAS or AAS instances in this cluster:

   [root]# export LD_LIBRARY_PATH=/usr/sap/<SID>/D<instance>/exe && \
   /usr/sap/<SID>/D<instance>/exe/sapstartsrv \
   pf=/usr/sap/<SID>/SYS/profile/<SID>_D<instance>_<as_virtual_hostname> \
   -reg

4. Disable the ASCS, ERS and any other application instance service that the cluster manages:

   [root]# systemctl disable SAP<SID>_<instance>.service
   Removed "/etc/systemd/system/multi-user.target.wants/SAP<SID>_<instance>.service".

   Run this using the ASCS instance number and repeat the command using the ERS instance number.

   Optional: Repeat the same for the PAS or AAS instance services.

5. Create the systemd drop-in directory for the ASCS, ERS and any other application instance service that the cluster manages:

   [root]# mkdir /etc/systemd/system/SAP<SID>_<instance>.service.d

   Run this using the ASCS instance number and repeat the command using the ERS instance number.

   Optional: Repeat using the PAS or AAS instance number.

6. Create the drop-in files for the instances in the new directory:

   [root]# cat << EOF > /etc/systemd/system/SAP<SID>_<instance>.service.d/HA.conf
   [Service]
   Restart=no
   EOF

   Run this using the ASCS instance number and repeat the command using the ERS instance number.

   Optional: Repeat using the PAS or AAS instance number.

7. Reload the systemd units to activate the drop-in configuration:

   [root]# systemctl daemon-reload

Verification

1. Check that all instances have instance systemd units and that they are disabled on the new node:

   [root]# systemctl list-unit-files SAPS4H*
   UNIT FILE         STATE    PRESET
   SAPS4H_20.service disabled disabled
   SAPS4H_29.service disabled disabled

   Optional: PAS or AAS instance service files are listed as well in all of the verification steps when you have configured the application server instances.

2. Check that the sapservices file contains entries for every instance on every cluster node:

   [root]# cat /usr/sap/sapservices
   systemctl --no-ask-password start SAPS4H_20 # sapstartsrv pf=/sapmnt/S4H/profile/S4H_ASCS20_s4hascs
   systemctl --no-ask-password start SAPS4H_29 # sapstartsrv pf=/sapmnt/S4H/profile/S4H_ERS29_s4hers

3. Check that all systemd configuration overrides are present:

   [root]# systemd-delta | grep SAP
   ...
   [EXTENDED]   /etc/systemd/system/SAPS4H_20.service  /etc/systemd/system/SAPS4H_20.service.d/HA.conf
   [EXTENDED]   /etc/systemd/system/SAPS4H_29.service  /etc/systemd/system/SAPS4H_29.service.d/HA.conf

Procedure

1. Install the Red Hat High Availability Add-On software packages from the High Availability repository. Choose the same fence agents as you have configured on the existing nodes and execute the installation on the new node:

   [root]# dnf install pcs pacemaker fence-agents-<model>

2. Start and enable the pcsd service:

   [root]# systemctl enable --now pcsd.service

3. Optional: If you are running the firewalld service, enable the ports that are required by the Red Hat High Availability Add-On:

   [root]# firewall-cmd --add-service=high-availability
   [root]# firewall-cmd --runtime-to-permanent

4. Set a password for the user hacluster:

   [root]# passwd hacluster

5. Authenticate the user hacluster for the new node in the existing cluster. Run this on an existing node, for example, node1:

   [root]# pcs host auth <node3>
   Username: hacluster
   Password:
   <node3>: Authorized

   • Enter the node names with or without FQDN, as defined in the /etc/hosts file.
   • Enter the hacluster user password in the prompt.

6. Add the new node to the existing cluster. This syncs cluster files between the nodes. Run this on an existing node, for example, node1:

   [root]# pcs cluster node add <node3>
   No addresses specified for host 'node3', using 'node3'
   Disabling sbd...
   node3: sbd disabled
   Sending 'corosync authkey', 'pacemaker authkey' to 'node3'
   node3: successful distribution of the file 'corosync authkey'
   node3: successful distribution of the file 'pacemaker authkey'
   Sending updated corosync.conf to nodes...
   node1: Succeeded
   node3: Succeeded
   node2: Succeeded
   node1: Corosync configuration reloaded

7. Start the cluster on the new node. Run this on the new node, for example, node3:

   [root]# pcs cluster start
   Starting Cluster...

8. Enable the cluster to be started automatically on system start, which enables the corosync and pacemaker services. Skip this step if you prefer to manually control the start of the cluster after a node restarts. Run on the new node:

   [root]# pcs cluster enable