This is another follow-up on the T-SQL exercise.   So the test query below is rather simple:   DBCC DROPCLEANBUFFERS go SELECT COUNT(*) FROM dbo.test;   But beneath its simple appearance, many factors are at play and interact in a complex way to influence the query performance. In other words, trying to predict its ...

Lies, damned lies, and statistics!   If you have read my three previous posts (1, 2, 3), you may walk away with an impression that on a drive presented from a high-end enterprise class disk array, Windows file fragmentation does not have a significant performance impact. And I’ve given you empirical data—oh yeah, statistics—to support that ...

256KB Sequential Reads   In my two previous posts (1, 2), I highlighted the fact that while file fragmentation had a huge adverse performance impact on directly attached storage (DAS), it did not have much, if any, impact on the drive presented from a high end enterprise class disk array. That observation was derived from running disk I/O ...