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SUSE Linux Enterprise Server for SAP Applications 12

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

SUSE® Linux Enterprise Server for SAP Applications is optimized in various ways for SAP* applications. This document explains how to deploy an S/4 HANA Enqueue Replication 2 High Availability Cluster solution. It is based on SUSE Linux Enterprise Server for SAP Applications 12 and related service packs.

Author: Fabian Herschel, Distinguished Architect SAP, SUSE
Author: Bernd Schubert, SAP Solution Architect, SUSE
Publication Date: 2020-02-25

1 About This Guide

1.1 Introduction

SUSE® Linux Enterprise Server for SAP Applications is the optimal platform to run SAP* applications with high availability. Together with a redundant layout of the technical infrastructure, single points of failure can be eliminated.

SAP* Business Suite is a sophisticated application platform for large enterprises and mid-size companies. Many critical business environments require the highest possible SAP* application availability.

The described cluster solution can be used for SAP* SAP S/4HANA ABAP Platform.

SAP S/4HANA ABAP Platform is a common stack of middleware functionality used to support SAP business applications. The SAP Enqueue Replication Server 2 constitutes application level redundancy for one of the most crucial components of the SAP S/4HANA ABAP Platform stack, the enqueue service. An optimal effect of the enqueue replication mechanism can be achieved when combining the application level redundancy with a high availability cluster solution, as provided for example by SUSE Linux Enterprise Server for SAP Applications. Over several years of productive operations, the components mentioned have proven their maturity for customers of different sizes and industries.

1.2 Additional Documentation and Resources

Several chapters in this document contain links to additional documentation resources that are either available on the system or on the Internet.

For the latest product documentation updates, see https://documentation.suse.com/.

More whitepapers, guides and best practices documents referring to SUSE Linux Enterprise Server and SAP can be found and downloaded at the SUSE Best Practices Web page:

https://documentation.suse.com/sbp/all/

Here you can access guides for SAP HANA system replication automation and High Availability (HA) scenarios for SAP NetWeaver and SAP S/4HANA.

Additional resources, such as customer references, brochures or flyers, can be found at the SUSE Linux Enterprise Server for SAP Applications resource library:

https://www.suse.com/products/sles-for-sap/#resource .

1.3 Errata

To deliver urgent smaller fixes and important information in a timely manner, the Technical Information Document (TID) for this document will be updated, maintained and published at a higher frequency:

1.4 Feedback

Several feedback channels are available:

Bugs and Enhancement Requests

For services and support options available for your product, refer to http://www.suse.com/support/.

To report bugs for a product component, go to https://scc.suse.com/support/ requests, log in, and select Submit New SR (Service Request).

Mail

For feedback on the documentation of this product, you can send a mail to doc-team@suse.com. Make sure to include the document title, the product version and the publication date of the documentation. To report errors or suggest enhancements, provide a concise description of the problem and refer to the respective section number and page (or URL).

2 Scope of This Document

The document at hand explains how to:

  • Plan a SUSE Linux Enterprise High Availability platform for SAP S/4HANA ABAP Platform, including SAP Enqueue Replication Server 2.

  • Set up a Linux high availability platform and perform a basic SAP S/4HANA ABAP Platform installation including SAP Enqueue Replication Server 2 on SUSE Linux Enterprise.

  • Integrate the high availability cluster with the SAP control framework via sap-suse-cluster-connector version 3, as certified by SAP.

Note
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”).

3 Overview

This document describes setting up a pacemaker cluster using SUSE Linux Enterprise Server for SAP Applications 12 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:

  • Integration of the cluster with the SAP start framework sapstartsrv to ensure that maintenance procedures do not break the cluster stability.

  • Rolling Kernel Switch (RKS) awareness.

  • Standard SAP installation to improve support processes.

  • Support of automated HA maintenance mode for SAP resources by implementing support of SAP HACheckMaintenanceMode and HASetMaintenanceMode.

  • Support of more than two cluster nodes for ASCS and ERS instances allowed.

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.

3.1 Differences to Previous Cluster Architectures

  • The described new concept differs from the old stack that used a master-slave architecture. With the new certification there is a switch to a simpler model with primitives. This means: on one machine there is the ASCS instance with its own resources and on the other machine there is the ERS instance with its own resources.

  • For SAP S/4HANA the new concept implies that, after a resource failure, the ASCS does not need to be started at the ERS side. The new enqueue architecture is also named ENSA2.

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
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.

SVG
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.

SVG
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 12

Intel X86_64

SAP HANA DATABASE 2.0

Note
Note

Version for SAP S/4HANA ABAP Platform on Linux on AMD64/Intel 64. 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
Note

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

SVG
Figure 3: Cluster connector to integrate the cluster with the SAP start framework
Note
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.

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 DB 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
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

3.6 IP Addresses and Virtual Names

Check if the file /etc/hosts contains at least the following address resolutions. Add those entries if they are missing.

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
  • 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.

SVG
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
Note

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

4 SAP Installation

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

Tasks
  1. Plan Linux user and group number scheme

  2. Install the ASCS instance for the central services

  3. Install the ERS to get a replicated enqueue scenario

  4. Prepare the ASCS and ERS installations for the cluster take-over

  5. Install the database

  6. Install the primary application server instance (PAS)

  7. Install additional application server instances (AAS)

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

SVG
Figure 5: Distributed installation of the SAP system

4.1 Linux User and Group Number Scheme

Whenever asked by the SAP software provisioning manager (SWPM) which Linux User IDs or Group IDs to use, refer to the following table as an example:

Group sapinst      1001
Group sapsys       1002
Group dbhshm       1003

User  en2adm       2001
User  sapadm       2002
User  dbhadm       2003

4.2 Installing ASCS on valuga11

Temporarily, as the local IP address, set the service IP address which you will later use in the cluster, because the installer needs to be able to resolve and use it. Make sure to use the correct virtual host name for each installation step. If applicable, make sure to also mount file systems like /dev/disk/by-id/SUSE-Example-A-part2 and /var/lib/Landscape/.

# 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
  • SWPM product installation path:

    • Installing SAP S/4HANA Server 1809 → SAP HANA DATABASE → Installation → Application Server ABAP → High-Availability System → ASCS Instance

  • Use SID EN2

  • Use instance number 00

  • Deselect using FQDN

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

  • Double-check during the parameter review, if virtual name sapen2as is used

4.3 Installing ERS on valuga12

Temporarily, as the local IP address, set the service IP address which you will later use in the cluster, because the installer needs to be able to resolve and use it. Make sure to use the correct virtual host name for each installation step.

# 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
  • SWPM product installation path:

    • Installing SAP S/4HANA Server 1809 → SAP HANA DATABASE → Installation → Application Server ABAP → High-Availability System → ERS Instance

  • Use instance number 10

  • Deselect using FQDN

  • Double-check during the parameter review that virtual name sapen2er is used

  • If you get an error during the installation about permissions, change the ownership of the ERS directory

# chown -R en2adm:sapsys /usr/sap/EN2/ERS10
  • If you get a prompt to manually stop/start the ASCS instance, log in to valuga11 as user en2adm and call 'sapcontrol'.

# 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 Maintaining sapservices

Ensure /usr/sap/sapservices holds both entries (ASCS and ERS) on both cluster nodes. This allows the sapstartsrv clients to start the service as follows:

As user en2adm, type the following command:

# sapcontrol -nr 10 -function StartService EN2

The /usr/sap/sapservices file looks as follows - typically one line per instance is displayed:

#!/bin/sh
LD_LIBRARY_PATH=/usr/sap/EN2/ASCS00/exe:$LD_LIBRARY_PATH; export LD_LIBRARY_PATH; /usr/sap/EN2/ASCS00/exe/sapstartsrv pf=/usr/sap/EN2/SYS/profile/EN2_ASCS00_sapen2as -D -u en2adm
LD_LIBRARY_PATH=/usr/sap/EN2/ERS10/exe:$LD_LIBRARY_PATH; export LD_LIBRARY_PATH; /usr/sap/EN2/ERS10/exe/sapstartsrv pf=/usr/sap/EN2/ERS10/profile/EN2_ERS10_sapen2er -D -u en2adm

If entries are missing you can register them using sapstartsrv with options pf=<profile-of-the-sap-instance> and -reg.

# 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

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
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.

service/halib = $(DIR_CT_RUN)/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

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

4.5 Installing Database on valuga01

The HANA DB has very strict HW requirements. The storage sizing depends on many indicators. Check the supported configurations at SAP HANA Hardware Directory and SAP HANA TDI.

# 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
  • SWPM product installation path:

    • Installing SAP S/4HANA Server 1809 → SAP HANA DATABASE → Installation → Application Server ABAP → High-Availability System → Database Instance

  • Profile directory /sapmnt/EN2/profile

  • Deselect using FQDN

  • Database parameters : Database ID (DBSID) is DBH; Database Host is sapen2db; Instance Number is 00

  • Database System ID enter Instance Number is 00; SAP Mount Directory is /sapmnt/EN2/profile

  • Account parameters: change them in case of custom values needed

  • Clean-up: select Yes, remove operating system users from the group sapinst.

  • Double-check during the parameter review, if virtual name sapen2db is used

4.6 Install the Primary Application Server (PAS) on valuga01

# 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
  • SWPM product installation path:

    • Installing SAP S/4HANA Server 1809 → SAP HANA DATABASE → Installation → Application Server ABAP → High-Availability System → Primary Application Server Instance

  • Use instance number 01

  • Deselect using FQDN

  • For this example setup we have used a default secure store key

  • Do not install Diagnostic Agent

  • No SLD

  • Double-check during the parameter review, if virtual name sapen2d1 is used

4.7 Installing an Additional Application Server (AAS) on valuga01

# 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
  • SWPM product installation path:

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

  • Use instance number 02

  • Deselect using FQDN

  • Do not install Diagnostic Agent

  • Double-check during the parameter review, if virtual name sapen2d2 is used

5 Implementing the Cluster

The main procedure to implement the cluster is as follows:

Tasks
  1. OS preparation and install the cluster software

  2. Configure the cluster base including corosync and resource manager

  3. Configure the cluster resources

  4. Tune the cluster timing in special for the SBD.

Note
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
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.

5.1 OS Preparation and Cluster Software Installation

  • Set up and enable NTP with yast2.

  • Install the RPM pattern ha_sles on both cluster nodes.

    # zypper in -t pattern ha_sles

5.2 Configuring the Cluster Base

Tasks
  • To configure the cluster base, you can use either YaST or the interactive command line tool ha-cluster-init. The example below uses the command line wizard.

  • Install and configure the watchdog device on the first machine.

Instead of deploying the software based solution, a hardware-based watchdog device should preferably be used. 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)"
  • Install and configure the cluster stack on the first machine

# ha-cluster-init -u -s  /dev/disk/by-id/SUSE-Example-A-part1
  • Join the second node

On the second node, perform some preparation steps.

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

To configure the cluster base, you can use either YaST or the interactive command line tool ha-cluster-join. The example below uses the command line wizard.

# ha-cluster-join -c valuga11
  • The crm_mon -1r output should look as follows:

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 master-slave construct anymore. Move to a more cluster-like construct to start and stop the ASCS and the ERS instances themselves, but not the complete master-slave.

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.

SVG
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.

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 \
  operations $id=rsc_sap_EN2_ASCS00-operations \
  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
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 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 \
  operations $id=rsc_sap_EN2_ERS10-operations \
  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
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"

6 Administration

6.1 Dos and Don’ts

Note
Note

Before each test, verify that the cluster is in idle state, no migration constraints are active, and no resource failure messages are visible. Start each procedure with a clean setup.

6.1.1 Migrating the ASCS Instance

To migrate the ASCS SAP instance, you should use SAP tools such as the SAP management console. This will trigger sapstartsrv to use the sap-suse-cluster-connector to migrate the ASCS instance. As user en2adm you can run the command below to migrate the ASCS. This will always migrate the ASCS to the ERS side which will keep the SAP enqueue locks.

As user en2adm, type the command:

# sapcontrol -nr 00 -function HAFailoverToNode ""

6.1.2 Never Block Resources

With SAP S/4-HA-CLU 1.0 it is no longer allowed to block resources from being controlled manually. This means using the variable BLOCK_RESOURCES in /etc/sap_suse_cluster_connector is not allowed anymore.

6.1.3 Always Use Unique Instance Numbers

Currently all SAP instance numbers controlled by the cluster must be unique. If you need multiple dialog instances, such as D00, running on different systems, they should not be controlled by the cluster.

6.1.4 Setting the Cluster to Maintenance Mode

The procedure to set the cluster into maintenance mode can be executed as user root or sidadm.

As user root, type the following command:

# crm configure property maintenance-mode="true"

As user en2adm, type the following command (the full path is needed):

# /usr/sbin/crm configure property maintenance-mode="true"

6.1.5 Stopping the Cluster Maintenance

The procedure to end the maintenance mode for the cluster can be executed as user root. Type the following command:

# crm configure property maintenance-mode="false"

6.1.6 Starting the Resource Maintenance Mode

The procedure to start the resource maintenance mode can be executed as user en2adm. This sets the ASCS and ERS cluster resource to unmanaged.

As user en2adm, type the command:

# sapcontrol -nr 00 -function HASetMaintenanceMode 1

6.1.7 Stopping the Resource Maintenance Mode

The procedure to start the resource maintenance mode can be executed as user en2adm. This sets the ASCS and ERS cluster resource to managed.

As user en2adm, type the command:

# sapcontrol -nr 00 -function HASetMaintenanceMode 0

6.1.8 Cleaning Up Resources

You can also clean-up resource failures. Failures of the ASCS will be automatically deleted to allow a failback after the configured period of time. For all other resources, you can clean-up the status including the failures.

As user root, type the following command:

# crm resource cleanup RESOURCE-NAME

6.2 Testing the Cluster

It is strongly recommended to perform at least the following tests before you go into production with your cluster:

6.2.1 Checking Product Names with HAGetFailoverConfig

Check if the name of the SUSE cluster solution is shown in the output of sapcontrol or the SAP management console. This test checks the status of the SAP NetWeaver cluster integration.

As user en2adm, type the following command:

# sapcontrol -nr 00 -function HAGetFailoverConfig

6.2.2 Running SAP Checks Using HACheckConfig and HACheckFailoverConfig

Check if the HA configuration tests are passed successfully and do not produce error messages.

As user en2adm, type the following commands:

# sapcontrol -nr 00 -function HACheckConfig
# sapcontrol -nr 00 -function HACheckFailoverConfig

6.2.3 Manually Migrating ASCS

Check if manually migrating the ASCS instance using HA tools works properly.

As user root, run the following commands:

# crm resource migrate rsc_sap_EN2_ASCS00 force
## wait until the ASCS is been migrated to the ERS host
# crm resource unmigrate rsc_sap_EN2_ASCS00

6.2.4 Migrating ASCS Using HAFailoverToNode

Check if moving the ASCS instance using SAP tools like sapcontrol works properly.

As user en2adm, type the following command:

# sapcontrol -nr 00 -function HAFailoverToNode ""

6.2.5 Test ASCS Migration After OS Failure

Check if the ASCS instance moves correctly after a node failure. This test will immediately trigger a hard reboot of the node.

As user root, type the following command:

## on the ASCS host
# echo b >/proc/sysrq-trigger

6.2.6 Restarting ASCS In-Place Using Stop and Start

Check if the in-place restart of the SAP resources have been processed correctly. The SAP instance should not failover to an other node, it must start on the same node where it has been stopped.

As user en2adm, do the following:

## example for ASCS
# sapcontrol -nr 00 -function Stop
## wait till the ASCS is completely down
# sapcontrol -nr 00 -function Start

6.2.7 Automated Restart of the ASCS Instance (Simulating Rolling Kernel Switch)

The next test should proof that the cluster solution did nor interact neither try to restart the ASCS instance during a maintenance procedure. In addition, it should verify that no locks are lost during the restart of an ASCS instance during an RKS procedure. The cluster solution should recognize that the restart of the ASCS instance was expected. No failure or error should be reported or counted.

Optionally, you can set locks and verify that they still exist after the maintenance procedure. There are multiple ways to do that. One example test can be performed as follows:

  1. Log in to your SAP system and open the transaction SU01.

  2. Create a new user. Do not finish the transaction to see the locks.

  3. With the SAP MC / MMC, check if there are locks available.

  4. Open the ASCS instance entry and go to Enqueue Locks.

  5. With the transaction SM12, you can also see the locks.

Do this test multiple times in a short time frame. The restart of the ASCS instance in the example below happens five times.

As user en2adm, create and execute the following script:

$ cat ascs_restart.sh
#!/bin/bash
for lo in 1 2 3 4 5; do
  echo LOOP "$lo - Restart ASCS00"
  sapcontrol -host sapen2as -nr 00 -function StopWait 120 1
  sleep 1
  sapcontrol -host sapen2as -nr 00 -function StartWait 120 1
  sleep 1
done
$ bash ascs_restart.sh

6.2.8 Rolling Kernel Switch Procedure

The rolling kernel switch (RKS) is an automated procedure that enables the kernel in an ABAP system to be exchanged without any system downtime. During an RKS, all instances of the system, and generally all SAP start services (sapstartsrv), are restarted.

  1. Check in SAP note 953653 whether the new kernel patch is RKS compatible to your currently running kernel.

  2. Check SAP note 2077934 - Rolling kernel switch in HA environments.

  3. Download the new kernel from the SAP service market place.

  4. Make a backup of your current central kernel directory.

  5. Extract the new kernel archive to the central kernel directory.

  6. Start the RKS via SAP MMC, system overview (transaction SM51) or via command line.

  7. Monitor and check the version of your SAP instances with the SAP MC / MMC or with sapcontrol.

As user en2adm, type the following commands:

## sapcontrol [-user <sidadm psw>] -host <host> -nr <INSTANCE_NR> -function UpdateSystem 120 300 1
# sapcontrol -user en2adm <use-your-secure-pwd> -host sapen2as -nr 00 -function UpdateSystem 120 300 1
# sapcontrol -nr 00 -function GetSystemUpdateList -host sapen2as \
  -user en2adm <use-your-secure-pwd>
# sapcontrol -nr 00 -function GetVersionInfo -host sapen2as \
  -user en2adm <use-your-secure-pwd>
# sapcontrol -nr 10 -function GetVersionInfo -host sapen2er \
  -user en2adm <use-your-secure-pwd>
# sapcontrol -nr 01 -function GetVersionInfo -host sapen2d1 \
  -user en2adm <use-your-secure-pwd>
# sapcontrol -nr 02 -function GetVersionInfo -host sapen2d2 \
  -user en2adm <use-your-secure-pwd>

6.2.9 Additional Tests

In addition to the already performed tests, you should do the following:

  • Check the recoverable and non-recoverable outage of the message server process.

  • Check the non-recoverable outage of the SAP enqueue server process.

  • Check the outage of the SAP Enqueue Replication Server 2.

  • Check the outage and restart of sapstartsrv.

  • Check the simulation of an upgrade.

  • Check the simulation of cluster resource failures.

7 Multi-Node Cluster Setups for an SAP S/4HANA

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 decribed different here to get a diskless SBD setup.

7.1 Extend An Existing Two Node Cluster Configuration

Tasks
  1. Backup the current cluster

  2. OS installation new node

  3. Patching the existing nodes

  4. Preparing the New Node’s Operating System

  5. SAP preparation

  6. Installing the cluster software on the new node

  7. joining the cluster

  8. Test the new cluster configuration

7.1.1 Backup the Current Cluster

Backup the current. cluster

  • Backup your system

    • 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.

Backing 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
# crm report

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 \
      <crm report files>
      <add your additional files here>

7.1.2 OS Installation 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 NTP Client (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.

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
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
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
  • Create the file /usr/sap/sapservices or copy it from one of your existing cluster nodes.

    Note
    Note

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

    The following commans register the ASCS and the ERS SAP instance:

    ##  create them with sapstartsrv
    # 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
  • Alternatively copy the file

    # scp -p valuga11:/usr/sap/sapservices /usr/sap/
  • Finally check the file

    # cat /usr/sap/sapservices
    #!/bin/sh
    LD_LIBRARY_PATH=/usr/sap/EN2/ASCS00/exe:$LD_LIBRARY_PATH; export LD_LIBRARY_PATH; /usr/sap/EN2/ASCS00/exe/sapstartsrv pf=/usr/sap/EN2/SYS/profile/EN2_ASCS00_sapen2as -D -u en2adm
    LD_LIBRARY_PATH=/usr/sap/EN2/ERS10/exe:$LD_LIBRARY_PATH; export LD_LIBRARY_PATH; /usr/sap/EN2/ERS10/exe/sapstartsrv pf=/usr/sap/EN2/SYS/profile/EN2_ERS10_sapen2er -D -u en2adm
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 ha-cluster-join

# ha-cluster-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

7.1.7 Test 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.

7.2 Pro’s and Con’s for Odd and Even Numbers of Cluster Nodes

There are certain use cases and infrastructure requirements which end up in different installation setup’s. We will cover some advantages and disadvantages of special configuration below:

  • The two node cluster and two locations

    • Advantage: symmetric spread of all nodes over all locations

    • Disadvantage: no diskless SBD feature allowed for all two node clusters

  • The two node cluster and more than two locations

    • Advantage: SBD device can be provided from there (must be HA himself)

    • Advantage: cluster could operate with three SBD devices from different locations

    • Disadvantage: no diskless SBD feature allowed for all two node clusters

  • The three node cluster and two locations

    • Advantage: less complex infrastructure

    • Advantage: diskless SBD feature is allowed

    • Disadvantage: "pre selected" location (two node + one node)

  • The three node cluster and three locations

    • Advantage: symmetric spread of all nodes over all locations

    • Advantage: diskless SBD feature is allowed

    • Disadvantage: higher planing effort and complexity for infrastructure planning

8 References

For more information, see the documents listed below.

9 Appendix

9.1 CRM Configuration

Find below the complete crm configuration for SAP system EN2. This example is for the two node cluster. In multi node cluster you will find additonal node entries like node 3: valuga13.

node 1: valuga11
node 2: valuga12
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_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_ASCS00 IPaddr2 \
    params ip=192.168.1.112 \
    op monitor interval=10s timeout=20s
primitive rsc_ip_EN2_ERS10 IPaddr2 \
    params ip=192.168.1.113 \
    op monitor interval=10s timeout=20s
primitive rsc_sap_EN2_ASCS00 SAPInstance \
    operations $id=rsc_sap_EN2_ASCS00-operations \
    op monitor interval=11 timeout=60 on-fail=restart \
    params InstanceName=EN2_ASCS00_sapen2as \
    START_PROFILE="/sapmnt/EN2/profile/EN2_ASCS00_sapen2as" \
    AUTOMATIC_RECOVER=false \
    meta resource-stickiness=5000
primitive rsc_sap_EN2_ERS10 SAPInstance \
    operations $id=rsc_sap_EN2_ERS10-operations \
    op monitor interval=11 timeout=60 on-fail=restart \
    params InstanceName=EN2_ERS10_sapen2er \
    START_PROFILE="/sapmnt/EN2/profile/EN2_ERS10_sapen2er" \
    AUTOMATIC_RECOVER=false IS_ERS=true
primitive stonith-sbd stonith:external/sbd \
    params pcmk_delay_max=30s
group grp_EN2_ASCS00 rsc_ip_EN2_ASCS00 rsc_fs_EN2_ASCS00 \
    rsc_sap_EN2_ASCS00 \
    meta resource-stickiness=3000
group grp_EN2_ERS10 rsc_ip_EN2_ERS10 rsc_fs_EN2_ERS10 \
    rsc_sap_EN2_ERS10
colocation col_sap_EN2_not_both -5000: grp_EN2_ERS10 grp_EN2_ASCS00
order ord_sap_EN2_first_ascs Optional: rsc_sap_EN2_ASCS00:start \
    rsc_sap_EN2_ERS10:stop symmetrical=false
property cib-bootstrap-options: \
    have-watchdog=true \
    cluster-infrastructure=corosync \
    cluster-name=hacluster \
    stonith-enabled=true \
    placement-strategy=balanced
rsc_defaults rsc-options: \
    resource-stickiness=1 \
    migration-threshold=3
op_defaults op-options: \
    timeout=600 \
    record-pending=true

9.2 Corosync Configuration of the Two Node Cluster

Find below the Corosync configuration.

# cat /etc/corosync/corosync.conf
# Please read the corosync.conf.5 manual page
totem {
    version: 2
    secauth: on
    crypto_hash: sha1
    crypto_cipher: aes256
    cluster_name: hacluster
    clear_node_high_bit: yes
    token: 5000
    token_retransmits_before_loss_const: 10
    join: 60
    consensus: 6000
    max_messages: 20
    interface {
        ringnumber: 0
        mcastport: 5405
        ttl: 1
    }

    transport: udpu
}

logging {
    fileline: off
    to_stderr: no
    to_logfile: no
    logfile: /var/log/cluster/corosync.log
    to_syslog: yes
    debug: off
    timestamp: on
    logger_subsys {
        subsys: QUORUM
        debug: off
    }

}

nodelist {
    node {
        ring0_addr: 192.168.1.103
        nodeid: 1
    }

    node {
        ring0_addr: 192.168.1.104
        nodeid: 2
    }

}

quorum {

    # Enable and configure quorum subsystem (default: off)
    # see also corosync.conf.5 and votequorum.5
    provider: corosync_votequorum
    expected_votes: 2
    two_node: 1
}

9.3 Corosync Configuration of the multi Node Cluster

	# Please read the corosync.conf.5 manual page
	totem {
		version: 2
		secauth: on
		crypto_hash: sha1
		crypto_cipher: aes256
		cluster_name: hacluster
		clear_node_high_bit: yes
		token: 5000
		token_retransmits_before_loss_const: 10
		join: 60
		consensus: 6000
		max_messages: 20
		interface {
			ringnumber: 0
			mcastport: 5405
			ttl: 1
		}

		transport: udpu
	}

	logging {
		fileline: off
		to_stderr: no
		to_logfile: no
		logfile: /var/log/cluster/corosync.log
		to_syslog: yes
		debug: off
		timestamp: on
		logger_subsys {
			subsys: QUORUM
			debug: off
		}

	}

	nodelist {
		node {
			ring0_addr: 192.168.1.103
			nodeid: 1
		}

		node {
			ring0_addr: 192.168.1.104
			nodeid: 2
		}

		node {
			ring0_addr: 192.168.1.105
			nodeid: 3
		}

	}

	quorum {

		# Enable and configure quorum subsystem (default: off)
		# see also corosync.conf.5 and votequorum.5
		provider: corosync_votequorum
		expected_votes: 3
		two_node: 0
	}
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