md Raid10 incorrectly asks for at least four devices

[Thimo E]

The issue seems to be this line:
https://github.com/CanonicalLtd/subiquity/blob/master/subiquity/models/filesystem.py#L157

Actually the minimum number of devices for md raid level 10 is 2.
This has some importance since raid10 - compared to raid1 - features roughly double read speed as long as only one thread is reading from disk.

[Michael Hudson-Doyle (mwhudson)]

Yes, seems you are right. I hate the raid documentation :)

[Thimo E (thimo-e)]

Actually, it seems the best description of RAID10 is on Wikipedia:
https://en.wikipedia.org/wiki/Non-standard_RAID_levels#Linux_MD_RAID_10

I can confirm this is my understanding of the linux-raid mailinglist.