dm-multipath without round robin

Hi Heinz.

I'm awfully sorry for directly asking for help to you, but I'm cranking my
head on an issue you might have an immediate answer for.

By default, dm-mpath-selector seems to always does round-robin between all
paths.

Is there a way to do simple failover instead or round-robin, ie. define a
preferred path and keep the other one as a spare?

It seems possible with md multipath, but then there is no way to create an
DM RAID0 over these md devices.

Hope you can help,

       -Frank.