Merge pull request #286793 from rdeltcheva/clock-src2

Add a section on supported clock sources in Azure VMs

Author: prmerger-automator[bot]

articles/sap/workloads/get-started.md

@@ -6,7 +6,7 @@ ms.service: sap-on-azure
 author: msjuergent
 manager: bburns
 ms.topic: article
-ms.date: 09/03/2024
+ms.date: 09/16/2024
 ms.author: juergent
 ---
 
@@ -55,6 +55,7 @@ In the SAP workload documentation space, you can find the following areas:
 
 ## Change Log
 
+- September 16, 2024: Included section on supported clock sources in Azure VMs in [SAP HANA infrastructure configurations and operations on Azure](./hana-vm-operations.md)
 - September 03, 2024: Included Mv3 High Memory and Very High Memory in HANA storage configuration in [SAP HANA Azure virtual machine Premium SSD storage configurations](./hana-vm-premium-ssd-v1.md), [SAP HANA Azure virtual machine Premium SSD v2 storage configurations](./hana-vm-premium-ssd-v2.md), and [SAP HANA Azure virtual machine Ultra Disk storage configurations](./hana-vm-ultra-disk.md)
 - August 22, 2024: Added documentation option for SAPHanaSR-angi as separate tab in [High availability for SAP HANA on Azure VMs on SLES](./sap-hana-high-availability.md) and [High availability of SAP HANA scale-up with Azure NetApp Files on SLES](./sap-hana-high-availability-netapp-files-suse.md).
 - July 29, 2024: Changes in [Azure VMs high availability for SAP NetWeaver on SLES for SAP Applications with simple mount and NFS](./high-availability-guide-suse-nfs-simple-mount.md), [Azure VMs high availability for SAP NW on SLES with NFS on Azure Files](./high-availability-guide-suse-nfs-azure-files.md), [Azure VMs high availability for SAP NW on SLES with NFS on Azure Files](./high-availability-guide-suse-netapp-files.md), [Azure VMs high availability for SAP NetWeaver on SLES](./high-availability-guide-suse.md), [Azure VMs high availability for SAP NetWeaver on SLES multi-SID guide](./high-availability-guide-suse-multi-sid.md) with the instructions of managing SAP ASCS and ERS instances SAP startup framework when configured with systemd.

articles/sap/workloads/hana-vm-operations.md

@@ -6,7 +6,7 @@ manager: bburns
 ms.service: sap-on-azure
 ms.subservice: sap-vm-workloads
 ms.topic: article
-ms.date: 11/09/2023
+ms.date: 09/16/2024
 ms.author: juergent
 ms.custom: H1Hack27Feb2017
 ---
@@ -53,7 +53,7 @@ Deploy the VMs in Azure by using:
 - Azure PowerShell cmdlets.
 - The Azure CLI.
 
-You also can deploy a complete installed SAP HANA platform on the Azure VM services through the [SAP Cloud platform](https://cal.sap.com/). The installation process is described in [Deploy SAP S/4HANA or BW/4HANA on Azure](./cal-s4h.md).
+You also can deploy a complete installed SAP HANA platform on the Azure VM services through the [SAP Cloud platform](https://cal.sap.com). The installation process is described in [Deploy SAP S/4HANA or BW/4HANA on Azure](./cal-s4h.md).
 
 >[!IMPORTANT]
 > In order to use M208xx_v2 VMs, you need to be careful selecting your Linux image. For more information, see [Memory optimized virtual machine sizes](/azure/virtual-machines/mv2-series).
@@ -105,6 +105,12 @@ To deploy SAP HANA in Azure without a site-to-site connection, you still want to
 Another description on how to use Azure NVAs to control and monitor access from Internet without the hub and spoke VNet architecture can be found in the article [Deploy highly available network virtual appliances](/azure/architecture/reference-architectures/dmz/nva-ha).
 
 
+### Clock source options in Azure VMs
+SAP HANA requires reliable and accurate timing information to perform optimally. Traditionally Azure VMs running on Azure hypervisor used only Hyper-V TSC page as a default clock source. Technology advancements in hardware, host OS and Linux guest OS kernels made it possible to provide "Invariant TSC" as a clock source option on some Azure VM SKUs.  
+
+Hyper-V TSC page (`hyperv_clocksource_tsc_page`)  is supported on all Azure VMs as a clock source. 
+If the underlying hardware, hypervisor and guest OS linux kernel support Invariant TSC, `tsc` will be offered as available and supported clock source in the guest OS on Azure VMs.    
+
 ## Configuring Azure infrastructure for SAP HANA scale-out
 
 In order to find out the Azure VM types that are certified for either OLAP scale-out or S/4HANA scale-out, check the [SAP HANA hardware directory](https://www.sap.com/dmc/exp/2014-09-02-hana-hardware/enEN/#/solutions?filters=v:deCertified;iaas;ve:24). A checkmark in the column 'Clustering' indicates scale-out support. Application type indicates whether OLAP scale-out or S/4HANA scale-out is supported. For details on nodes certified in scale-out, review the entry for a specific VM SKU listed in the SAP HANA hardware directory.