I suspect largely an artifact is "the substrate lists it" mixed with "people sometimes require odd RAID configurations based upon specific need/use case, and that is not really something we should restrict."

That being said, personally I have never configured a RAID2 in my career, nor RAID3.

RAID0, 1, 4 (once), 5, 6, 1+0, 5+0, 5+1, 6+0: Sure.

Given 2 and 3 are for bit level striping, not block level, I suspect nobody would cry if we remove them.

-Julia

On Thu, Dec 14, 2023 at 2:07 AM Dmitry Tantsur <dtantsur@protonmail.com> wrote:

Hi folks,

I was going through our RAID support and noticed that we declare support
for RAID level 2. Per wikipedia [1] it's an extremely rarely used level
which offers little benefits. Does anyone remember why we use that? Will
anyone cry if we drop it?

My worry is officially supporting something that nobody can even test
because of lack of hardware or real use case behind it.

Dmitry

[1] https://en.wikipedia.org/wiki/Standard_RAID_levels#RAID_2