Hello,

It seems to me that IostallMs is not related to Number of Bytes Reads/Writes

but to the number of Read/Writes

So the last select, should be

SELECT TOP 5

DataBaseName,

TimeStamp,

SUM(NumberReads) + SUM(NumberWrites) AS NBIORequests,

SUM(IoStallMS) AS IoStallMS,

SUM(IoStallMS) / (SUM(NumberReads) + SUM(NumberWrites)) AS IOStallRatio

FROM

tempdb.dbo.tbl_DatabaseFileStats

GROUP BY

DataBaseName,TimeStamp

ORDER BY

IOStallRatio DESC