Clustering SAP ASCS Instance using Windows Server Failover Cluster on Microsoft Azure with SIOS DataKeeper and Azure Internal Load Balancer
Published Mar 13 2019 10:30 AM 2,331 Views
First published on MSDN on May 20, 2015

We released new white paper on clustering SAP ASCS instance using Windows Server Failover Cluster on Microsoft Azure public cloud.

It describes how to install and configure a high-availability (HA) SAP central services instance ASCS in a Windows Failover Cluster (WSFC) using the platform Microsoft Azure.

The SAP central services instance for ABAP (SAP ASCS instance) together with the database instance is a single point of failure (SPOF) in an SAP system. The availability of the ASCS instance is essential for the high availability of an SAP system.

At this point in time Azure on itself would not be able to provide the functionality to set up the required Windows Server Failover Cluster in a native manner.

As of April 2015 the Azure cloud platform running the Windows operating system does not provide the possibility of using:

  • A cluster shared volume

  • Multiple virtual IP addresses

WSFC cluster shared volume in Windows Azure

However you can create a Windows server failover cluster shared volume with a 3rd party software SIOS DataKeeper Cluster Edition, which is needed to install and cluster SAP ASCS instance on the Azure IaaS platform.

The SIOS DataKeeper solution provides a shared disk cluster resource to Windows Failover Cluster by having:

  • An additional Azure VHD attached to each of the virtual machines (VMs) that are in a Windows Cluster configuration

  • SIOS DataKeeper Cluster Edition running on both VM nodes

  • Having SIOS DataKeeper Cluster Edition configured in a way that it synchronous mirrors the content of the additional VHD attached volume from source VMs to additional VHD attached volume of target VM.

  • SIOS DataKeeper is abstracting the source and target local volumes and presenting them to Windows Failover Cluster as a single shared disk.

WSFC virtual IP addresses in Windows Azure

In an on-premise solution the DNS-Server routes the traffic with a virtual IP-address to the active Cluster node. On Azure we use the Azure Internal Load Balancer (ILB) to route the traffic to the cluster node where SAP ASCS instance is running.

Figure 1: Schema of a Windows Server Failover Cluster configuration in Azure using SIOS DataKeeper and Azure Internal Load Balancer (ILB)


Support of Windows Server Failover Cluster on Windows Azure Cloud

SIOS DataKeeper Cluster Edition Certification on Windows Azure Cloud

Running SAP Applications on the Microsoft Platform Blog

White Papers: Using SAP on Azure Virtual Machines (VMs)

Azure Internal Load Balancer

DataKeeper Cluster Edition

TCP/IP Ports Used by SAP Applications

SAP Notes:

Note number



SAP Applications on Azure: Supported Products and Sizing


SAP on Microsoft Azure: Support Prerequisites


Enhanced Azure Monitoring for SAP


Virtualization on Windows: Enhanced Monitoring

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