Synchronous replicas in SQL Server Availability Groups promise no data loss, but they don’t promise zero delay; under heavy load they can still fall behind. This article shows how to measure and track that hidden replication delay using SQL Server performance counters, so you can see how well your system keeps up during IO‑intensive operations and plan maintenance more safely.
Why Measure Latency?
Availability Groups are useful for creating Highly Available (HA) database systems, but that doesn’t mean they are entirely immune to performance problems. In busy systems, limitations in the infrastructure can introduce replication lag that is severe enough