https://docs.microsoft.com/en-us/sql/sql-server/failover-clusters/high-availability-solutions-sql-server?view=sql-server-2017
https://blogs.msdn.microsoft.com/alwaysonpro/
https://docs.microsoft.com/en-us/sql/sql-server/failover-clusters/windows/windows-server-failover-clustering-wsfc-with-sql-server?view=sql-server-2017
https://blogs.msdn.microsoft.com/psssql/tag/alwayson/
https://blogs.msdn.microsoft.com/saponsqlserver/2015/10/23/sql-server-alwayson-summary/
https://blogs.msdn.microsoft.com/psssql/2011/04/01/alwayson-hadron-learning-series-how-does-alwayson-process-a-synchronous-commit-request/
https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/availability-group-lease-healthcheck-timeout?view=sql-server-2017
https://blogs.msdn.microsoft.com/clustering/2009/06/26/what-is-rhs-and-what-does-it-do/
https://blogs.msdn.microsoft.com/psssql/2012/09/07/how-it-works-sql-server-alwayson-lease-timeout/
https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/availability-group-lease-healthcheck-timeout?view=sql-server-2017
https://blogs.msdn.microsoft.com/saponsqlserver/2012/02/07/sql-server-2012-alwayson-what-is-it/
https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/overview-of-always-on-availability-groups-sql-server?view=sql-server-2017
https://blogs.msdn.microsoft.com/clustering/2009/09/04/failover-clustering-performance-counters-part-1/