I'm overseeing an Always On Availability Group (AG) setup in SQL Server, configured with five servers. One server functions as the quorum disk, with the remaining servers designated as primary and secondary replicas. To maintain time consistency across all servers, we utilize an NTP server. Recently, we've encountered scenarios where the NTP server becomes inaccessible, leading to all servers' clocks being erroneously set to the year 2028. This has raised concerns about the potential impact on our system, specifically regarding log synchronization between the primary and secondary replicas.

Problem Description:

Given the critical role of accurate timekeeping in transaction log management and replication within SQL Server AGs, I am concerned about the implications of these time discrepancies. I understand that SQL Server uses time stamps to order transactions and ensure consistency across replicas, but I am unsure about the extent to which time synchronization issues might affect the reliability of our AG setup.

Specific Questions:

Impact on Log Synchronization: How does a significant time discrepancy, such as an incorrect jump to the year 2028, affect the synchronization of logs between servers and replicas within an Always On Availability Group? Are there mechanisms within SQL Server that can mitigate the effects of such discrepancies on log replication and application?

Dependency on NTP Server: Is there a direct dependency on the NTP server or accurate server time for the proper functioning of the Always On Availability Group synchronization process? In other words, can time discrepancies lead to failures in transaction log replay or issues with maintaining the health of the AG?

Mitigation Strategies: What are best practices for mitigating risks associated with time synchronization failures in a SQL Server AG environment? Are there recommended configurations or redundancy measures to ensure that time discrepancies do not compromise data integrity or availability?

I am looking for insights, experiences, or recommendations on managing and mitigating the impact of time synchronization issues in SQL Server Always On Availability Groups. Any advice on configuring our environment to handle such anomalies, or understanding the underlying mechanisms that SQL Server uses to deal with time discrepancies, would be greatly appreciated.


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