Hello @Jay Kim ,
Thank you for reaching out to the Microsoft Q&A platform. Happy to answer your question.
As per your update, I understand you have specified the log backup frequency is set to every one hour in the backup policy like below.
Please note that all the scheduled backups and on-demand backups (triggered from the Azure portal) that are either full or differential are initiated by the Azure Backup Plugin for HANA. However, log backups are managed and triggered by HANA Backup Engine itself.
About your assumption of log backup schedule to be triggered sharp 7 am or 8 am is not correct. The backup intervals are always based on the start time/end time of the last successful backup. If the log backup was at the very first is triggered at say 7:30 or 7:45 am the next schedule of the log backup becomes 8:30 am or 8:45 am.
In your case I see the log backup time is conflicting with your VMs reboot time. VM is shut down during the operation
Azure backups have the logic to detect this in Fabric Service to get the VM running status and mark the operation a "User Error if the VM was found shut down. But, if the VM is shutting down during the operation, ARM keeps reporting the VM as running for some time and hence the operation fails with error similar to "WorkloadExtensionNotReachable". It is helpful to check the error message reported for the failed log backups and refer to the following document
Suggestion: Based on the log backup start/end time in the backup job history, it will be good to re-adjust the VM reboot schedule by noting the total time taken to reboot the VM.
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@Prrudram-MSFT any further comment?