[ggm]

Say you have a 2, 2x4s and an 8. You should be able to have almost everything mirrored or have some raidz2 and some raidz1.

[magicalhippo]

You could mirror them, then you could use all the space.

Not sure I see how you'd do a raidz2+raidz1 combo using those drives, at least not without losing 4TB of the 8TB drive, but then I'm tired so.