[CentOS] CentOS 7 : create RAID arrays manually using mdadm --create ?

[Chris Murphy]

On Mon, Feb 9, 2015 at 5:16 PM, Niki Kovacs <info at microlinux.fr> wrote:
> Hi,
>
> When installing CentOS 7, is there a way to
>
> 1. leave the GUI installer and open up a console
> 2. create RAID arrays manually using mdadm --create
> 3. get back in the GUI installer and use the freshly created /dev/mdX
> arrays?
>
> I tried to do this, but the installer always exits informing me that he
> can't create the RAID arrays (since they're already created, duh).
>
> Any suggestions?

It's useful to know what layout you want. The installer will neither
create, nor let you use, what it thinks are ill-advised layouts. The
main reason I can think of for pre-creating md devices is to use a
non-default chunk/strip size.

The other thing is if you want to use LVM on top of an md device, I'm
pretty sure you have to create the whole thing in advance because the
installer UI won't add LVM on top of an existing md device. It expects
that you create a mount point, define it as an LVM device, then within
the modify options you choose what RAID type you want, which you can't
do if the md device is already created.

Anyway, it's a lot easier if you just state what you want first. And
then it's also useful to understand the installer's UI is mount point
centric, it kinda deemphasizes the specifics of how that mount point
gets assembled.

-- 
Chris Murphy