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


2 Answers 2

  • 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.


I was watching this excellent talk on PASS - "Finding root cause for unexplained Availability Group failover", by Trayce Jordan.

In that he mentions that the lease timeout mechanism is there for extra redundancy to extra make sure that we do not get into a split brain situation.

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