Implementing HA SAP NetWeaver with AnyDB on Azure VMs (part 2)

 

To read part 1 please click here



Add registry entries on both cluster nodes of the SAP ASCS-SCS instance

If you want to add registry entries on both cluster nodes of the SAP ASCS-SCS instance, then you have to add them on both Windows cluster nodes for SAP ASCS/SCS:

Path

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Variable name

KeepAliveTime

Variable type

REG_DWORD (Decimal)

Value

120000

Path

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Variable name

KeepAliveTime

Variable type

REG_DWORD (Decimal)

Value

120000

 You have to restart both the cluster nodes to apply the changes. 

Set up a Windows Server failover cluster for SAP ASCS-SCS instance

It involves the following tasks:

  • Add cluster nodes to the cluster.
  • Configure Cloud witness 

Add cluster nodes to the cluster

You have to set up the failover cluster by using the Failover Cluster Manager:

  • In the Failover Cluster Manager, select Create Cluster, and then add only the name of the first cluster.
  • Enter the network name (virtual host name) of the cluster.
  • After successfully creating the cluster, you have to run a validation test.
  • At this point you can ignore the warnings about disks and should not worry about having a quorum.
  • Bring the cluster virtual host name online.
  • Now you can add the second cluster node.

Configure cloud witness

If you want to configure the cloud witness, then you should have a valid Azure Storage Account through which you can store the blob file (used for arbitration). The same Microsoft Storage Account can be used to configure a Cloud Witness for multiple different clusters and will contain one-blob file per cluster. When creating a storage account, you should keep in mind that:
  • You can't use a Blob storage account for a Cloud Witness.
  • You can't use Azure Premium Storage for a Cloud Witness.
  • For replication, select Locally-redundant Storage (LRS) because the Failover Clustering uses the blob file as the arbitration point, which in turn also requires some consistency guarantees while reading the data. 

Note- No extra steps are required for the configuration necessary for the URL as the endpoint is generated automatically by Cloud Witness resource.

Configure failover parameters

After successfully installing the Windows Failover Clusters, you  should change some thresholds, so that they can adapt to the conditions in Azure for failover detection. If you assume that your two VMs consisting teh cluster configuration for ASCS/SCS are in the same subnet, then you can easily change the following parameters to these values:

  • SameSubNetDelay = 2000
  • SameSubNetThreshold = 15
  • RoutingHistoryLength = 30

Although all these settings are resilient enough, but they can also offer failover that is fast enough in real error conditions on a SAP atmosphere or in a node or VM failure. 



To read part 1 please click here




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