VIRTUAL FILE STATS - Any idea why a particualr server would be "bouncing" statistics?
*** This DOES NOT appear related to the sample_ms column issue ***
- Process collects sys.dm_io_virtual_file_stats and writes to custom table, on 15 min interval. This has been running since last Tuesday, using SQL Server Agent Job.
- This occurs for multiple databases and multiple files, but for READS ONLY. WRITES appear to increment.
- The same type of data is present in the custom table, or if I query the data directly out of sys.dm_io_virtual_file_stats.
- The server just "rolled over" sample_ms column, but this was occuring previously.
- I validated the elapsed time based on delta of insertdate in the custom table and by delta of sample_ms.
- Configuration: 10.50.2500.0 / 128GB / 24 lproc / 64-bit
- Server is new to our group. It is SAN attached (no details yet).
SAMPLE DATA.
The query properly joins a recorded copy of VFS to determine the previous record for the same DB/FileID. Notice how the READ values (CNT, BYTES, STALL) will decrement between subsequent recordings, then return back
InsertDatetime RID sample_ms ---------READ------------ --------WRITE------------
CNT BYTES STALL CNT BYTES STALL
---------------- ----- ----------- ----- ---------- -------- ----- ---------- --------
2013-08-20 15:30 221 1851413611 62 3948544 785 0 0 0
2013-08-20 15:45 369 1852313363 62 3948544 785 0 0 0
2013-08-20 16:00 517 1853213161 57 3620864 827 0 0 0
2013-08-20 16:15 663 1854113349 61 3883008 882 0 0 0
2013-08-20 16:30 811 1855013428 61 3883008 882 0 0 0
2013-08-20 16:45 959 1855913086 61 3883008 882 0 0 0
2013-08-20 17:00 1107 1856812884 57 3620864 1212 0 0 0
2013-08-20 17:15 1255 1857712978 61 3883008 1258 0 0 0
2013-08-20 17:30 1403 1858613073 61 3883008 1258 0 0 0
2013-08-20 17:45 1551 1859513167 61 3883008 1258 0 0 0
2013-08-20 18:00 1699 1860412435 57 3620864 975 0 0 0
2013-08-20 18:15 1847 1861312655 61 3883008 1010 0 0 0
2013-08-20 18:30 1995 1862212749 61 3883008 1010 0 0 0
2013-08-20 18:45 2143 1863112953 61 3883008 1010 0 0 0
2013-08-20 19:00 2291 1864013079 54 3424256 955 0 0 0
2013-08-20 19:15 2437 1864912237 61 3883008 1033 0 0 0 