Our newly installed and configured SQL Server Always On Availability Failover Cluster with SQL Server 2016 Enterprise Edition runs with four instances and six nodes. It includes the DB Engine Service and the Agent Service in each Cluster Node's resources. Everything works fine.
But now we figured that the fill-text Filter Daemon Launcher (FTFDL) service exists on each of the nodes and is randomly running, independant if the fact where the Sql-Instance is currently running. Some nodes have four FTFDL services running, while only one instance is located there. Others have one or two of them running.
Question: Should we add this service as a cluster resource? Why is it getting started and stopped abviously randomly on the failover cluster instances resutling in multiple services active without the relevant instance active? What is best practice here?