TL;DR: Zentyal Software RAID Setup.

Unfortunately it isn’t all that easy or straight forward for a targeted server disto to easily allow

1. Start Install in ‘Expert’ mode.
2. Go through install until you get to partitions.
3. Select the partitioning method as ‘Manual’.
4. First create ’empty’ partitions on each drive (I actually did this within PartedMagic).
5. Then create the Software RAID (I created 1 MD device with RAID 1).
6. Then you can create the LVM partitions (I used the Guided Partition step to automatically create everything, otherwise you can do it manually by hand).

Thanks to Rafaelwolf.com