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Prepare Azure infrastructure for SAP high availability by using a Windows failover cluster and file share for SAP ASCS/SCS instances

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This article describes the Azure infrastructure preparation steps that are needed to install and configure high-availability SAP systems on a Windows Server Failover Clustering cluster (WSFC), using scale-out file share as an option for clustering SAP ASCS/SCS instances.

Prerequisite

Before you start the installation, review the following article:

Host names and IP addresses

Virtual host name role Virtual host name Static IP address Availability set
First cluster node ASCS/SCS cluster ascs-1 10.0.6.4 ascs-as
Second cluster node ASCS/SCS cluster ascs-2 10.0.6.5 ascs-as
Cluster network name ascs-cl 10.0.6.6 n/a
SAP PR1 ASCS cluster network name pr1-ascs 10.0.6.7 n/a

Table 1: ASCS/SCS cluster

SAP <SID> SAP ASCS/SCS instance number
PR1 00

Table 2: SAP ASCS/SCS instance details

Virtual host name role Virtual host name Static IP address Availability set
First cluster node sofs-1 10.0.6.10 sofs-as
Second cluster node sofs-2 10.0.6.11 sofs-as
Third cluster node sofs-3 10.0.6.12 sofs-as
Cluster network name sofs-cl 10.0.6.13 n/a
SAP global host name sapglobal Use IPs of all cluster nodes n/a

Table 3: Scale-Out File Server cluster

Deploy VMs for an SAP ASCS/SCS cluster, a Database Management System (DBMS) cluster, and SAP Application Server instances

To prepare the Azure infrastructure, complete the following:

Deploy the Scale-Out File Server cluster manually 

You can deploy the Microsoft Scale-Out File Server cluster manually, as described in the blog Storage Spaces Direct in Azure, by executing the following code:  

# Set an execution policy - all cluster nodes
Set-ExecutionPolicy Unrestricted

# Define Scale-Out File Server cluster nodes
$nodes = ("sofs-1", "sofs-2", "sofs-3")

# Add cluster and Scale-Out File Server features
Invoke-Command $nodes {Install-WindowsFeature Failover-Clustering, FS-FileServer -IncludeAllSubFeature -IncludeManagementTools -Verbose}

# Test cluster
Test-Cluster -node $nodes -Verbose

# Install cluster
$ClusterNetworkName = "sofs-cl"
$ClusterIP = "10.0.6.13"
New-Cluster -Name $ClusterNetworkName -Node $nodes –NoStorage –StaticAddress $ClusterIP -Verbose

# Set Azure Quorum
Set-ClusterQuorum –CloudWitness –AccountName gorcloudwitness -AccessKey <YourAzureStorageAccessKey>

# Enable Storage Spaces Direct
Enable-ClusterS2D

# Create Scale-Out File Server with an SAP global host name
# SAPGlobalHostName
$SAPGlobalHostName = "sapglobal"
Add-ClusterScaleOutFileServerRole -Name $SAPGlobalHostName

Deploy Scale-Out File Server automatically

You can also automate the deployment of Scale-Out File Server by using Azure Resource Manager templates in an existing virtual network and Active Directory environment.

Important

We recommend that you have three or more cluster nodes for Scale-Out File Server with three-way mirroring.

In the Scale-Out File Server Resource Manager template UI, you must specify the VM count.

Use managed disks

The Azure Resource Manager template for deploying Scale-Out File Server with Storage Spaces Direct and Azure Managed Disks is available on GitHub.

We recommend that you use Managed Disks.

Figure 1: UI screen for Scale-Out File Server Resource Manager template with managed disks

Figure 1: UI screen for Scale-Out File Server Resource Manager template with managed disks

In the template, do the following:

  1. In the Vm Count box, enter a minimum count of 2.
  2. In the Vm Disk Count box, enter a minimum disk count of 3 (2 disks + 1 spare disk = 3 disks).
  3. In the Sofs Name box, enter the SAP global host network name, sapglobalhost.
  4. In the Share Name box, enter the file share name, sapmnt.

Use unmanaged disks

The Azure Resource Manager template for deploying Scale-Out File Server with Storage Spaces Direct and Azure Unmanaged Disks is available on GitHub.

Figure 2: UI screen for the Scale-Out File Server Azure Resource Manager template without managed disks

Figure 2: UI screen for the Scale-Out File Server Azure Resource Manager template without managed disks

In the Storage Account Type box, select Premium Storage. All other settings are the same as the settings for managed disks.

Adjust cluster timeout settings

After you successfully install the Windows Scale-Out File Server cluster, adapt timeout thresholds for failover detection to conditions in Azure. The parameters to be changed are documented in Tuning failover cluster network thresholds. Assuming that your clustered VMs are in the same subnet, change the following parameters to these values:

  • SameSubNetDelay = 2000
  • SameSubNetThreshold = 15
  • RouteHistoryLength = 30

These settings were tested with customers, and offer a good compromise. They are resilient enough, but they also provide fast enough failover in real error conditions or VM failure.

Next steps