You can find more information on querying the DMVs for this information in SQLPerformance's Monitoring Availability Group Replica Synchronization. This is the query from the article (with one additional calculated column to get you the Estimated Recovery Time:

This article also briefly mentions a third way to monitor these metrics via Perfmon Counters.

You can find more information on querying the DMVs for this information in SQLPerformance's Monitoring Availability Group Replica Synchronization. This is the query from the article (with one additional calculated column to get you the Estimated Recovery Time):

The above article also briefly mentions a third way to monitor these metrics via Perfmon Counters.

And finally a third and equally effective way to log your Availability Groups health metrics is via the built-in Extended Events.

If you want to access this information more natively so you can collect the metrics over time, the above Availability Group Dashboard just leverages the following DMVs:

1. sys.dm_hadr_database_replica_states
2. sys.availability_databases_cluster
3. sys.availability_groups
4. sys.availability_replicas

You can find more information on querying the DMVs for this information in SQLPerformance's Monitoring Availability Group Replica Synchronization. This is the query from the article (with one additional calculated column to get you the Estimated Recovery Time:

SELECT 
    ar.replica_server_name, 
    adc.database_name, 
    ag.name AS ag_name, 
    drs.is_local, 
    drs.is_primary_replica, 
    drs.synchronization_state_desc, 
    drs.is_commit_participant, 
    drs.synchronization_health_desc, 
    drs.recovery_lsn, 
    drs.truncation_lsn, 
    drs.last_sent_lsn, 
    drs.last_sent_time, 
    drs.last_received_lsn, 
    drs.last_received_time, 
    drs.last_hardened_lsn, 
    drs.last_hardened_time, 
    drs.last_redone_lsn, 
    drs.last_redone_time, 
    drs.log_send_queue_size, 
    drs.log_send_rate, 
    drs.redo_queue_size, 
    drs.redo_rate, 
    drs.redo_queue_size / see.redo_rate AS EstimatedRecoveryTime -- Additional helpful calculated column
    drs.filestream_send_rate, 
    drs.end_of_log_lsn, 
    drs.last_commit_lsn, 
    drs.last_commit_time
FROM sys.dm_hadr_database_replica_states AS drs
INNER JOIN sys.availability_databases_cluster AS adc 
    ON drs.group_id = adc.group_id AND 
    drs.group_database_id = adc.group_database_id
INNER JOIN sys.availability_groups AS ag
    ON ag.group_id = drs.group_id
INNER JOIN sys.availability_replicas AS ar 
    ON drs.group_id = ar.group_id AND 
    drs.replica_id = ar.replica_id
ORDER BY 
    ag.name, 
    ar.replica_server_name, 
    adc.database_name;

You can create a SQL job to routinely log this information to a table so you have a historical comparison to achieve your goals with. (This is essentially what RedGate's Performance Monitor is likely doing under the hood.)

This article also briefly mentions a third way to monitor these metrics via Perfmon Counters.