SQL Alwayson availabity group latency We have sql server 2014 alwayson availability group set up for a database. Synchronous-commit availability mode is used. We ran a few PAL (Performance Analyzer Log) reports to obtain performance data on the primary replica and they showed IO alerts where read and writes were >25ms. The IO alerts occurred for both logical and physical IOs and on drives C:, F: (that has db files) and L: (that has transaction logs). I ran this statement: 

SELECT 
    wait_type, waiting_tasks_count, wait_time_ms,
    wait_time_ms/waiting_tasks_count as 'time_per_wait'
FROM 
    sys.dm_os_wait_stats 
WHERE 
    waiting_tasks_count &gt; 0
    and wait_type = 'HADR_SYNC_COMMIT';


and got 12ms for the time_per_wait value. This means the latency between the primary and secondary replicas were 12 ms.

My question: does the IO response time reported by PAL include this 12ms latency between the primary and the secondary replicas?

Thanks
According to PSS that wait type is the time it takes for the primary to receive a notification that the log block has been written on the destination (though not replayed), and after this the wait type changes to WRITELOG and the log block gets written locally.

Logically then any disk waits to write the block remotely must be included in that HADR_SYNC_COMMIT time.

Perhaps if you run PAL on your secondary you will see that it has lower disk latency and so can complete the writes faster. It would be interesting for you to look and see.

Incidentally the MSSQL Tiger Team have a video and demo XE script and Power BI sample that gathers AG sync information and displays it in graphs; if you're interested in exploring that you could give it a try.