Next we build a RAID1 array, i.e. a “mirror”.

Alas, the speed of this array may degenerate, too, with enabled TCQ. And the number of red-colored cells seems to reach a maximum. You can observe a speed gain at read requests only.

We might have supposed that we would have a smaller “average” load on each disk when there are more disks in the array because the load on the array is evenly distributed among all of its drives. And accordingly, we would have worse results with enabled TCQ since the range of “inconvenient” loads becomes wider. That’s true – we do see the results worsening at max loads, but the speed loss at small loads becomes smaller! It seems like the reduction of the load rate helps the drives to do their job better…