Add a section on supported clock sources in Azure VMs

Author: rdeltcheva

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
 ---
@@ -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.