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

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

The document at hand explains how to:

Note

This guide implements the cluster architecture for enqueue replication version 2. For SAP S/4HANA ABAP Platform versions 1809 or newer enqueue replication version 2 is the default.

This guide focuses on the high availability of the central services. For SAP HANA system replication consult the guides for the performance-optimized or cost-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 15 for the Enqueue Replication scenario. The focus is on matching the SAP S/4-HA-CLU 1.0 certification specifications and goals. For the setup described in this document, two nodes are used for the ASCS central services instance and ERS replicated enqueue instance. These two nodes are controlled by the SUSE Linux Enterprise High Availability cluster. A third node is used for running the database and PAS and AAS application server instances. An additional fourth node is used as NFS server.

The goals for the setup include:

The updated certification SAP S/4-HA-CLU 1.0 redefines some of the test procedures and describes new expectations how the cluster should behave in special conditions. These changes allowed to improve the cluster architecture and to design it for easier usage and setup.

Shared SAP resources are located on a central NFS server.

The SAP instances themselves are installed on a shared disk to allow for switching over the file systems for proper functionality. A shared disk setup also allows using the SBD for the cluster fencing mechanism STONITH.

3.2 Three systems or more for ASCS, ERS, database and additional SAP instances #

 

This document describes the installation of a distributed SAP system on three and more systems. In this setup, only two systems reside inside the cluster. The database and SAP dialog instances can be added to the cluster either by adding more nodes to the cluster or by installing the database on either of the existing nodes. However, it is recommended to install 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: Because the setup at hand focuses on the SAP S/4-HA-CLU 1.0 certification, the cluster detailed in this guide only manages the SAP instances ASCS and ERS.

If your database is SAP HANA, we recommend setting up the performance-optimized system replication scenario using the automation solution SAPHanaSR. The SAPHanaSR automation should be set up in an own two-node cluster. The setup is described in a separate best practices document available from the SUSE Best Practices Web page.

Figure 1: Three systems for the certification setup #

 

Clustered machines Two-Node Scenario #

 

• one machine (valuga11) for ASCS

  • Hostname: sapen2as

• one machine (valuga12) for ERS

  • Hostname: sapen2er

Non-Clustered machine #

 

• one machine (valuga01) for DB and as application server

  • Hostname: sapen2db

  • Hostname: sapen2d1

  • Hostname: sapen2d2

3.3 High availability for the database #

 

Depending on your needs, you can increase the availability of the database, if your database is not already highly available by design.

3.3.1 SAP HANA system replication #

 

A perfect enhancement of the three-node scenario described in this document is to implement an SAP HANA system replication (SR) automation.

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

 

Table 1: The following OS/database combinations are examples for this scenario #

 

SUSE Linux Enterprise Server for SAP Applications 15
Intel X86_64	SAP HANA DATABASE 2.0
IBM PowerLE	SAP HANA DATABASE 2.0

Note

Version for SAP S/4HANA ABAP Platform on Linux on AMD64/Intel 64 and PowerLE. More information about the supported combinations of OS and databases for SAP S/4HANA Server 1809 can be found at the SAP Product Availability Matrix at SAP PAM.

3.4 Integration of 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 since 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 interfaces provided by the cluster software, the cluster framework will detect that as an error status and will bring the SAP instance into the old status by either starting or stopping the SAP instance. 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 state changes to the cluster software. This avoids dangerous situations as previously described. More details can be found in 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/.

Note

If you update from an SAP S/4HANA ABAP Platform version less than 1809, read SAP Note 2641019 carefully to adapt your cluster.

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

 

Note

For this scenario, an updated 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 new 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 even the SAP management consoles (SAP MMC or SAP MC). Since version 3.1.0 and later the maintenance mode of cluster resources triggered with SAP sapcontrol commands is supported. See also manual page sap_suse_cluster_connector(8).

3.5 Disks and partitions #

 

XFS is used for all SAP file systems besides the file systems on NFS.

3.5.1 Shared disk for cluster ASCS and ERS #

 

The disk for the ASCS and ERS instances must be shared and assigned to the cluster nodes valuga11 and valuga12 in the two-node cluster example. In addition to the partitions for the file systems for the SAP instances, the disk also provides the partition to be used as SBD.

On valuga11 prepare the file systems for the shared disk. Create three partitions on the shared drive /dev/disk/by-id/SUSE-Example-A:

• Partition one (/dev/disk/by-id/SUSE-Example-A-part1) for SBD (7 MB)

• Partition two (/dev/disk/by-id/SUSE-Example-A-part2) for the first file system (10 GB) formatted with XFS

• Partition three (/dev/disk/by-id/SUSE-Example-A-part3) for the second file system (10 GB) formatted with XFS

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

Example 1: Create Partitions and File Systems for SBD and ASCS/ERS on valuga11 #

 

# parted -s /dev/disk/by-id/SUSE-Example-A print
# # we are on the 'correct' drive, right?
# parted -s /dev/disk/by-id/SUSE-Example-A mklabel gpt
# parted -s /dev/disk/by-id/SUSE-Example-A mkpart primary 1049k 8388k
# parted -s /dev/disk/by-id/SUSE-Example-A mkpart primary 8389k 10.7G
# parted -s /dev/disk/by-id/SUSE-Example-A mkpart primary 10.7G 21.5G
# mkfs.xfs /dev/disk/by-id/SUSE-Example-A-part2
# mkfs.xfs /dev/disk/by-id/SUSE-Example-A-part3

For these file systems, we recommend using normal partitions to keep the cluster configuration as simple as possible. However, you can also place these file systems in separate volume groups. In that case, you need to add further cluster resources to control the logical volume groups, and occasionally MD-Raid devices. The description of such a setup however is out of the scope of this guide.

After having partitioned the shared disk on valuga11, you need to request a partition table rescan on valuga12.

# partprobe; fdisk -l /dev/disk/by-id/SUSE-Example-A

During the SAP installation you need to mount /usr/sap/EN2/ASCS00 on valuga11 and /usr/sap/EN2/ERS10 on valuga12.

• valuga11: /dev/disk/by-id/SUSE-Example-A-part2 /usr/sap/EN2/ASCS00

• valuga12: /dev/disk/by-id/SUSE-Example-A-part3 /usr/sap/EN2/ERS10

3.5.2 Disk for database and dialog instances (HANA DB) #

 

The disk for the database server is assigned to valuga01. The disk for the primary and secondary application server is assigned to valuga01.

valuga01 #

 

• Partition one (/dev/disk/by-id/SUSE-Example-B-part1) for the database (160 GB) formatted with XFS

• Partition two (/dev/disk/by-id/SUSE-Example-B-part2) for the PAS instance (10 GB) formatted with XFS

• Partition three (/dev/disk/by-id/SUSE-Example-B-part3) for the AAS instance (10 GB) 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 2: Create Partitions and File Systems for DB and App Servers on valuga01 #

 

# parted -s /dev/disk/by-id/SUSE-Example-B print
# # we are on the 'correct' drive, right?
# parted -s /dev/disk/by-id/SUSE-Example-B mklabel gpt
# parted -s /dev/disk/by-id/SUSE-Example-B mkpart primary 1049k 160G
# parted -s /dev/disk/by-id/SUSE-Example-B mkpart primary 160G 170G
# parted -s /dev/disk/by-id/SUSE-Example-B mkpart primary 170G 180G
# mkfs.xfs /dev/disk/by-id/SUSE-Example-B-part1
# mkfs.xfs /dev/disk/by-id/SUSE-Example-B-part2
# mkfs.xfs /dev/disk/by-id/SUSE-Example-B-part3

To be mounted either by OS or an optional cluster #

 

• valuga01: /dev/disk/by-id/SUSE-Example-B-part1 /hana

• valuga01: /dev/disk/by-id/SUSE-Example-B-part2 /usr/sap/EN2/D01

• valuga01: /dev/disk/by-id/SUSE-Example-B-part3 /usr/sap/EN2/D02

Note

D01: Since NetWeaver 7.5 the primary application server instance directory has been renamed to 'D<Instance_Number>'.

NFS server #

 

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

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

Media #

 

• 192.168.1.1:/Landscape /var/lib/Landscape

192.168.1.100  valuga01
192.168.1.103  valuga11
192.168.1.104  valuga12

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

3.7 Mount points and NFS shares #

 

In the present setup the directory /usr/sap is part of the root file system. You can also create a dedicated file system for that area and mount /usr/sap during the system boot. As /usr/sap contains the SAP control file sapservices and the saphostagent, the directory should not be placed on a shared file system between the cluster nodes.

You need to create the directory structure on all nodes that should run the SAP resource. The SYS directory will be located on an NFS share for all nodes.

• Create mount points and mounting NFS shares on all nodes.

Example 3: Mount NFS Shares on all nodes #

 

# mkdir -p /sapmnt /var/lib/Landscape
# mkdir -p /usr/sap/EN2/{ASCS00,D01,D02,ERS10,SYS}
# mount -t nfs 192.168.1.1:/data/export/S4_HA_CLU_10/EN2/sapmnt    /sapmnt
# mount -t nfs 192.168.1.1:/data/export/S4_HA_CLU_10/EN2/SYS /usr/sap/EN2/SYS
# mount -t nfs 192.168.1.1:/Landscape /var/lib/Landscape

Mount options may depend on your particular environment. See also manual page mount.nfs(8).

• For HANA: Create mount points for database at valuga01:

# mkdir /hana
# mount /dev/disk/by-id/SUSE-Example-B-part1 /hana/
# mkdir -p /hana/{shared,data,log}
# mount /dev/disk/by-id/SUSE-Example-B-part2 /usr/sap/EN2/D01
# mount /dev/disk/by-id/SUSE-Example-B-part3 /usr/sap/EN2/D02

You do not control the NFS shares via the cluster in the setup at hand. Thus you should add these file systems to /etc/fstab to get the file systems mounted during the next system boot.

Figure 4: File system layout including NFS shares #

 

Prepare the three servers for the distributed SAP installation. Server 1 (valuga01) is used to install the SAP HANA database. Server 1 (valuga01) is used to install the PAS SAP instance. Server 1 (valuga01) is used to install the AAS SAP instances. Server 2 (valuga11) is used to install the ASCS SAP instances. Server 3 (valuga12) is used to install the ERS SAP instances.

• Mount the instance and database file systems on one specific node:

Example 4: Mount several file systes for SAP S/4HANA on different nodes #

 

(ASCS   valuga11) # mount /dev/disk/by-id/SUSE-Example-A-part2 /usr/sap/EN2/ASCS00
(ERS    valuga12) # mount /dev/disk/by-id/SUSE-Example-A-part3 /usr/sap/EN2/ERS10
(DB     valuga01) # mount /dev/disk/by-id/SUSE-Example-B-part1 /hana/
(Dialog valuga01) # mount /dev/disk/by-id/SUSE-Example-B-part2 /usr/sap/EN2/D01
(Dialog valuga01) # mount /dev/disk/by-id/SUSE-Example-B-part2 /usr/sap/EN2/D02

• As a result, the directory /usr/sap/EN2/ should now look as follows:

# ls -la /usr/sap/EN2/
total 0
drwxr-xr-x 1 en2adm sapsys 70 28. Mar 17:26 ./
drwxr-xr-x 1 root   sapsys 58 28. Mar 16:49 ../
drwxr-xr-x 7 en2adm sapsys 58 28. Mar 16:49 ASCS00/
drwxr-xr-x 1 en2adm sapsys  0 28. Mar 15:59 D02/
drwxr-xr-x 1 en2adm sapsys  0 28. Mar 15:59 D01/
drwxr-xr-x 1 en2adm sapsys  0 28. Mar 15:59 ERS10/
drwxr-xr-x 5 en2adm sapsys 87 28. Mar 17:21 SYS/

Note

The owner of the directory and files is changed during the SAP installation. By default, all of them are owned by root.

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

The result will be a distributed SAP installation as illustrated here:

Figure 5: Distributed installation of the SAP system #

 

Group sapinst      1001
Group sapsys       1002
Group dbhshm       1003

User  en2adm       2001
User  sapadm       2002
User  dbhadm       2003

# ip a a 192.168.1.112/24 dev eth0
# mount /dev/disk/by-id/SUSE-Example-A-part2 /usr/sap/EN2/ASCS00
# cd /var/lib/Landscape/media/SAP-media/SWPM20_P9/
# ./sapinst SAPINST_USE_HOSTNAME=sapen2as

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

# ip a a 192.168.1.113/24 dev eth0
# mount /dev/disk/by-id/SUSE-Example-A-part3 /usr/sap/EN2/ERS10
# cd /var/lib/Landscape/media/SAP-media/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 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 Disabling systemd services of the ASCS and the ERS SAP instance #

 

This is mandatory for giving control over the instance to the 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 this 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_10.service disabled
SAPEN2_10.service 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 is still there for compatibility. It shows native systemd commands, one per line for each registered instance. You will find a SystemV style example in the appendix.

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

 

Install the package sap-suse-cluster-connector version 3.1.0 from the SUSE repositories:

# zypper in sap-suse-cluster-connector

Note

The package sap-suse-cluster-connector contains the version 3.x.x (SAP API 3). The package sap-suse-cluster-connector with version 3.0.x implements the SUSE SAP API version 3. New features like SAP Rolling Kernel Switch (RKS) and migration of ASCS are only supported with this new version. The package sap-suse-cluster-connector with version 3.1.x supports in addition the maintenance mode of cluster resources triggered from SAP tools.

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/.

Tell the sapstartsrv service to load the HA script connector library and to use the connector sap-suse-cluster-connector. Additionally, make sure 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).

4.4.4 Adapting SAP profiles to match the SAP S/4-HA-CLU 1.0 certification #

 

For the ASCS instance, change the start command from Restart_Program_xx to Start_Program_xx for the enqueue server (Enqueue Server 2). This change tells the SAP start framework not to self-restart the enqueue process. Such a restart would result in a loss of the 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)

4.4.5 Starting ASCS and ERS #

 

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

On valuga11, do the following:

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

On valuga12, do the following

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

# ip a a 192.168.1.114/24 dev eth0
# mount /dev/disk/by-id/SUSE-Example-B-part1 /hana
# mount /dev/disk/by-id/SUSE-Example-B-part2 /usr/sap/EN2/D01
# mount /dev/disk/by-id/SUSE-Example-B-part3 /usr/sap/EN2/D02
# cd /var/lib/Landscape/media/SAP-media/SWPM20_P9/
# ./sapinst SAPINST_USE_HOSTNAME=sapen2db

# ip a a 192.168.1.110/24 dev eth0
# mount /dev/disk/by-id/SUSE-Example-B-part2 /usr/sap/EN2/D01
# cd /var/lib/Landscape/media/SAP-media/SWPM20_P9/
# ./sapinst SAPINST_USE_HOSTNAME=sapen2d1

# ip a a 192.168.1.111/24 dev eth0
# mount /dev/disk/by-id/SUSE-Example-B-part3 /usr/sap/EN2/D02
# cd /var/lib/Landscape/media/SAP-media/SWPM20_P9/
# ./sapinst SAPINST_USE_HOSTNAME=sapen2d2

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

The SBD device/partition needs to be created beforehand. Double-check which device/partition to use! In this setup guide a partition /dev/disk/by-id/SUSE-Example-A-part1 is already 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)"

# ha-cluster-init -u -s  /dev/disk/by-id/SUSE-Example-A-part1

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

# ha-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 ]

stonith-sbd	(stonith:external/sbd):	Started valuga11

5.3 Configuring cluster resources #

 

A changed SAPInstance resource configuration is needed for SAP S/4HANA to not use the multi-state construct anymore. Move to a more cluster-like construct to start and stop the ASCS and the ERS instances themselves, but not the complete multi-state resource.

With the new version of ENSA2, the ASCS instance can be started on the same host. There is no longer a need to follow the ERS instance. The ASCS instance receives the enqueue lock table over the network from the ERS instance. If no other node is available, the ASCS instance will be started on the same host where the ERS instance is running.

Figure 6: Resources and constraints #

 

Another benefit of this concept is that you can work with native (mountable) file systems instead of a shared (NFS) file system for the SAP instance directories.

5.3.1 Preparing the cluster for adding the resources #

 

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

As user root, type the following command:

# crm configure property maintenance-mode="true"

5.3.2 Configuring the resources for the ASCS instance #

 

First, configure the resources for the file system, IP address and the SAP instance. You need to adapt the parameters for your specific environment. The shown file system and SAPInstance monitor timeouts are a trade-off between fast recovery vs. resilience against sporadic temporary NFS issues. You may slightly increase it to fit your infrastructure. The SAPInstance timeout needs to be higher than the file system timeout. Consult your storage or NFS server documentation for appropriate timeout values. See also manual pages ocf_heartbeat_Filesystem(7), ocf_heartbeat_SAPInstance(7) and nfs(5).

Example 5: ASCS primitive #

 

primitive rsc_fs_EN2_ASCS00 Filesystem \
  params device="/dev/disk/by-id/SUSE-Example-A-part2" directory="/usr/sap/EN2/ASCS00" \
         fstype=xfs \
  op start timeout=60s interval=0 \
  op stop timeout=60s interval=0 \
  op monitor interval=20s timeout=40s
primitive rsc_ip_EN2_ASCS00 IPaddr2 \
  params ip=192.168.1.112 \
  op monitor interval=10s timeout=20s
primitive rsc_sap_EN2_ASCS00 SAPInstance \
  op monitor interval=11 timeout=60 on-fail=restart \
  params InstanceName=EN2_ASCS00_sapen2as \
     START_PROFILE="/usr/sap/EN2/SYS/profile/EN2_ASCS00_sapen2as" \
     AUTOMATIC_RECOVER=false \
  meta resource-stickiness=5000

See also manual pages ocf_heartbeat_SAPInstance(7), ocf_heartbeat_IPaddr2(7) and ocf_heartbeat_Filesystem(7).

Example 6: ASCS group #

 

group grp_EN2_ASCS00 \
  rsc_ip_EN2_ASCS00 rsc_fs_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

5.3.3 Configuring the resources for the ERS instance #

 

Second, configure the resources for the file system, IP address and the SAP instance. You need to adapt the parameters for your specific environment. The shown file system and SAPInstance monitor timeouts are a trade-off between fast recovery versus resilience against sporadic temporary NFS issues. You may slightly increase it to fit your infrastructure. The SAPInstance timeout needs to be higher than the file system timeout. Consult your storage or NFS server documentation for appropriate timeout values. See also manual pages ocf_heartbeat_Filesystem(7), ocf_heartbeat_SAPInstance(7) and nfs(5).

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

Example 7: ERS primitive #

 

primitive rsc_fs_EN2_ERS10 Filesystem \
  params device="/dev/disk/by-id/SUSE-Example-A-part3" directory="/usr/sap/EN2/ERS10" fstype=xfs \
  op start timeout=60s interval=0 \
  op stop timeout=60s interval=0 \
  op monitor interval=20s timeout=40s
primitive rsc_ip_EN2_ERS10 IPaddr2 \
  params ip=192.168.1.113 \
  op monitor interval=10s timeout=20s
primitive rsc_sap_EN2_ERS10 SAPInstance \
  op monitor interval=11 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

See also manual pages ocf_heartbeat_SAPInstance(7), ocf_heartbeat_IPaddr2(7) and ocf_heartbeat_Filesystem(7).

Example 8: ERS group #

 

group grp_EN2_ERS10 \
  rsc_ip_EN2_ERS10 rsc_fs_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

# crm configure load update crm_ers.txt

5.3.4 Configuring the colocation constraints between ASCS and ERS #

 

Compared to the ENSA1 configuration, the constraints between the ASCS and ERS instances are changed. An ASCS instance should avoid starting up on the cluster node running the ERS instance if any other node is available. Today 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 take-over.

Example 9: Location constraint #

 

colocation col_sap_EN2_no_both -5000: grp_EN2_ERS10 grp_EN2_ASCS00
order ord_sap_EN2_first_start_ascs 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

5.3.5 Activating the cluster #

 

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

As user root, type the following command:

# crm configure property maintenance-mode="false"

Multinode cluster setups mean cluster configurations with more than two nodes. Depending from the starting point it is possible to extend a two node cluster setup or directly start with more than two nodes for an ASCS / ERS high availability setup. The examples below will show the setting up of Multi-node cluster and the extension of an existing two node cluster pair. The major configuration changes will be shown and the basic preparation of the new cluster member node.

The task list to set up the three node cluster is similar to the task list of the two node cluster. But some details are described different here to get a diskless SBD setup. Such a diskless SBD setup is an optional improvement for three nodes, but does not work for two nodes. On the other hand, priority fencing is an optional improvement for two nodes, but does not work for three nodes. Ssee the SUSE Linux Enterprise High Availability product documentation for details (https://documentation.suse.com/sle-ha/15-SP3/single-html/SLE-HA-administration/#pro-ha-storage-protect-fencing).

Note

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

7.1 Extending an existing two-node cluster configuration #

 

Tasks #

 

1. Back up the current cluster.

2. Install the OS on the new node.

3. Patch the existing nodes.

4. Prepare the new node’s operating system.

5. Prepare SAP.

6. Install the cluster software on the new node.

7. Joining the cluster.

8. Test the new cluster configuration.

7.1.1 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 - Setup Guide.

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

# crm configure save 2node.txt

Back up the existing /etc/corosync/corosync.conf and all other files which may be important for a restore. This example is one method creating a backup. The important point is using an external destination.

# tar cvf /<path to an external storage>/bck_2nodes_configuration.tar \
      /etc/corosync/corosync.conf \
      2node.txt \
      <add your additional files here>

7.1.2 Installing the operating system of the new cluster node member #

 

We recommend using automating the installation to ensure that the system setup across nodes is identical. Make sure to document any additional steps you take beyond the automated setup. In our example, we deploy our machines with an AutoYaST configuration file and run a post step script which does the basic configuration.

7.1.3 Patching 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 Manager, add the new system to the same repositories, so they have the same patch level as your existing nodes.

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

• It is recommended 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:

# zypper patch --category security
 or
# zypper patch --severity important
 or
# zypper patch
## or
# zypper update

7.1.4 Preparing the new node’s operating system #

 

Example 10: Check for valid DNS, time synchronization, network settings #

 

• Verify that DNS is working:

  # ping <hostname>

• Set up chrony (this is best done with YaST) 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.

7.1.5 Installing cluster software on the new node #

 

Example 11: Installing packages #

 

• Install the pattern ha_sles on the new cluster node:

  # zypper in -t pattern ha_sles

• Install the package sap-suse-cluster-connector version 3.1.0 from the SUSE repositories:

  # zypper in sap-suse-cluster-connector

After installing all necessary packages, compare installed package versions.

Example 12: Check that all nodes have the same software packages and versions #

 

• On the existing cluster nodes:

  # rpm -qa | sort >rpm_valuga11.log

• On the new node:

  # rpm -qa | sort >rpm_valuga13.log

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

  # vimdiff rpm_valuga13.log rpm_valuga11.log

Note

If there any differences fix them first before you proceed.

Example 13: Install and configure the watchdog device on the new machine. #

 

Instead of deploying the software-based solution, preferably 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 the same exact SBD configurations already exist on the two existing nodes

# sbd -d /dev/disk/by-id/SUSE-Example-A-part1 dump

7.1.6 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 will help us to prepare a new host which can later run either the ASCS or ERS in the cluster environment.

You need to create the directory structure that should run the SAP resource. The SYS directory is located on an NFS share for all nodes.

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

Example 14: Mount NFS Shares on valuga13 #

 

# mkdir -p /sapmnt /var/lib/Landscape
# mkdir -p /usr/sap/EN2/{ASCS00,ERS10,SYS}
# mount -t nfs 192.168.1.1:/data/export/S4_HA_CLU_10/EN2/sapmnt    /sapmnt
# mount -t nfs 192.168.1.1:/data/export/S4_HA_CLU_10/EN2/SYS /usr/sap/EN2/SYS
# mount -t nfs 192.168.1.1:/Landscape /var/lib/Landscape

As this directory needs to be available at all time, make sure it is mounted during boot. This can be achieved by put the information into the /etc/fstab.

In the next step the following information are required: - profile directory - password for SAP System Administrator - UID for sapadm

# cd /var/lib/Landscape/media/SAP-media/SWPM20_P9/
# ./sapinst

• SWPM product installation path:

  • Installing SAP S/4HANA Server 1809 → SAP HANA DATABASE → Installation → Application Server ABAP → High-Availability System → Prepare Additional Host

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

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

• UID for sapadm: 2002

Example 15: 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>_<virtHostNameA
  scs> -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

7.1.7 Adding the new node to the cluster #

 

Example 16: Add the New Node to the Cluster #

 

Check if the SBD device is available in case the SBD stonith method is in place for the two nodes. If the existing cluster using a different, supported stonith mechanism check and verify them too for the new cluster node.

# sbd -d /dev/disk/by-id/SUSE-Example-A-part1 dump

• Joining the cluster with sleha-join

# sleha-join -c valuga11

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

# grep votes -n2 /etc/corosync/corosync.conf

The values expected_votes and two_node should now look like this 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

7.1.8 Testing the new cluster configuration #

 

It is highly recommended to run certain test to verify that the new configuration is working as expected. A list of test can be found in the basic setup for the two node cluster above.

For more information, see the documents listed below.

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