Can not create Raid-Z 2 out of 4 identical discs

[Spacemarine]

I have 4 identical disks (WD red 3TB) and I want to create a Raid-Z 2 pool out of them. However, the GUI doesn't offer that option. Is this a bug? Am I doing something wrong?

 

[dlavigne]

Drag the slider so that all 4 are in the same row (currently it is splitting them into 2 rows).

 

[Spacemarine]

Thanks, that did the trick! I only moved the slider within the blue area, I never thought about moving it outside the blue box.