I have a mac mini with two internal disks. So far, I've been running them with appleRAID in a stripe. But... a) el capitain messes this up, b) no recovery partition possible, and c) I've had another problem that necessitated reloading from scratch.
Your doc says I should be able to boot from a softRAID volume and even be able to create a recovery partition on it, or on those disks.
How do I do that?
Even if I create a USB key, boot from it, include softRAID and create a new volume, that... a) won't have softRAID drivers, so how would it boot? and b) won't have a recovery partition.
So... how do I do that?
Recovery partitoins are not possible on any RAID volume. Create a USB bootable disk for that.
You can boot from a USB disk and set up your SoftRAID volume. You can install Yosemite or El Capitan right onto it. (Mavericks also, but there is a minor trick, the install file must be on an Apple formatted disk)
Everything will work fine!