I worked today on tuning a system and ran into something that I can’t explain. I wonder if anyone can help find what I am missing.
I have took snapshots of sys.dm_io_virtual_file_stats and calculated the deltas for 3 hour perod.
I could see ~1.7M reads that took ~400 minutes. The average latencies reported for the files were similar to what I could see when examining the physical
disks counter from perfmon.
However, when I examine sys.dm_os_wait_stats (again deltas for the same 3 hours) I could not see 1.7 I/O events.