Deployment Scheme

Figure 1 shows the processes of deploying SAP S/4HANA in HA mode.

Figure 1 SAP S/4HANA HA deployment flowchart

In this deployment mode, the SAP S/4HANA system consists of multiple SAP instances. An SAP instance is a group of processes that are simultaneously started or stopped. In the SAP S/4HANA system, each SAP instance is deployed on an ECS. The SAP instances include:

• ASCS instance
• Enqueue Replication Server instance (ERS instance)
• Database instance (DB instance)
• Primary Application Server instance (PAS instance)
• Additional Application Server instance (AAS instance)

Table 1 describes the feature of each SAP S/4HANA component.

Customers can install SAP S/4HANA as required and formulate deployment modes based on its component features to ensure HA. To avoid SPOF and ensure HA, the ASCS instance (including the Message server and Enqueue server) requires the cloud platform and the database is configured with the active and standby switchover. Central instance and Dialog instance (including the ABAP Dialog and Batch work process) can be installed on multiple ECSs to ensure HA.

Figure 2 shows the recommended HA deployment mode on the public cloud.

Figure 2 Recommended SAP S/4HANA HA deployment mode

The preceding describes an example of the SAP S/4HANA HA deployment mode. You can install SAP S/4HANA as required.

• ASCS instance (including the Message server and Enqueue server) is a system that may have an SPOF. With the help of the cloud platform, ASCS instance is protected from an SPOF. Two ASCS ECSs need to be created and attached with a shared disk. The ASCS and PAS instances are installed on the active ECS, and the ERS and AAS instances are installed on the standby ECS. The time synchronization and disk formatting must be performed on the two ECSs.
• For details about how to deploy SAP HANA in active/standby mode, see the Single-Node Scenario Where HA Is Required.
• The security group and elastic NICs are used to protect SAP S/4HANA Central instance, ASCS instance, and DB instance to avoid communication errors and isolate failed resources.
• Table 2 and Table 3 show the file system planning for the active and standby ASCS nodes.

  Table 2 File system planning for the active ASCS node

  Mount Point	File System Type	Description
  /usr/sap/<SID>/ASCS<##>	xfs NOTE: In the cross-AZ or cross-region scenario, this file system type is sfs.	Shared disk, which is used to install the ASCS instance. For details, see section Node Planning. In the cross-AZ/Region scenario, SFS Turbo provides shared disks.
  /sapmnt	sfs	SFS Turbo file system, which provides the shared storage. For details, see section Node Planning.
  /usr/sap/<SID>/SYS	sfs	SFS Turbo file system, which provides the shared storage. For details, see section Node Planning.
  /sapcd	sfs	SFS Turbo file system, which provides the shared storage. The SAP S/4HANA installation package is uploaded to this directory.

  Table 3 File system planning for the standby ASCS node

  Mount Point	File System Type	Description
  /usr/sap/<SID>/ERS<##>	xfs NOTE: In the cross-AZ or cross-region scenario, this file system type is sfs.	Shared disk, which is used to install the ERS instance. For details, see section Node Planning. In the cross-AZ/Region scenario, SFS Turbo provides shared disks.
  /sapmnt	sfs	SFS Turbo file system, which provides the shared storage. For details, see section Node Planning.
  /usr/sap/<SID>/SYS	sfs	SFS Turbo file system, which provides the shared storage. For details, see section Node Planning.
  /sapcd	sfs	SFS Turbo file system, which provides the shared storage. The SAP S/4HANA installation package is uploaded to this directory.