Sql-server – Lease Timeout VS HealthCheck Timeout – AlwaysON

availability-groupsclusteringsql serversql server 2014

After all the reading this is what I understood. Is it correct?

LeaseTimeout is a simple heartbeat between SQL Server resource DLL and the SQL Server instance.

HealthCheck Timeout is related to sp_server_diagnostics run.

Why do we have two timeouts?

Also how do I change the LeaseTimeout? Is it through the cluster manager because I couldnt find any T-SQL command like below for HealthCheck Timeout 

ALTER AVAILABILITY GROUP AG1 SET (HEALTH_CHECK_TIMEOUT = 40000);

Best Answer

  • The HealthCheck is between WSFC and SQL Server. The timeout is how long WSFC will wait to get data back from the sp_server_diagnostics execution.
  • LeaseTimeout is the SQL Server resource and SQL Server Availability Group. How Lease Timeout works

There are two timeouts because they are for 2 different mechanisms for health of the WSFC and SQL Server. Both are changed via the WSFC property of the AG resource, picture is shown in the linked article above.

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