Code review comment for ~mwhudson/curtin:raid-min-levels

I'm kinda -1 on this. Is there a launchpad bug for this?

From mdadm manpage:

-n, --raid-devices=
              Specify the number of active devices in the array. This, plus the number of spare devices (see below) must equal the number of component-devices (includ‐
              ing "missing" devices) that are listed on the command line for --create. Setting a value of 1 is probably a mistake and so requires that --force be spec‐
              ified first. A value of 1 will then be allowed for linear, multipath, RAID0 and RAID1. It is never allowed for RAID4, RAID5 or RAID6.

RAID5 without the third is missing the parity and is RAID1 AFAICT. Looking for sources to see where I'm wrong about that.

RAID10 with two disks will require (IMO) supporting layouts (which is good, but that's a feature add with testing I think).

https://marc.info/?l=linux-raid&m=141051176728630&w=2