Sladescross's Blog

Blogging about Sharepoint related stuff

Perfmon Averages versus sys.dm_io_virtual_file_stats for Disk Latency December 31, 2012

Filed under: Disk,Latency,PerfMon,sys.dm_io_virtual_file_stats — sladescross @ 8:05 pm

http://sqlblog.com/blogs/michael_zilberstein/archive/2012/11/28/46419.aspx

Finally we’ve found the answer after more thorough analysis of PerfMon file. It appears that calculation formula is different. sys.dm_io_virtual_file_stats contains total number of writes and total write latency (stall), so by dividing them we receive average latency per single write operation. PerfMon on another hand measure Disk sec/write counter every sample interval (default is 15 seconds, I used 1 second interval in order to see more detailed picture).

 

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