CentOS - Feb 2015 - CentOS 7 : create RAID arrays manually using mdadm --create ?

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?

Cheers,

Niki
-- 
Microlinux - Solutions informatiques 100% Linux et logiciels libres
7, place de l'?glise - 30730 Montpezat
Web  : http://www.microlinux.fr
Mail : info at microlinux.fr
T?l. : 04 66 63 10 32

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

On my first attempt doing this with 2x disk, GPT partition scheme,
precreated md devices, and LVM, rebooting, upon entering the installer
and choosing a language, I get a crash. Looks like it's this bug:
https://bugzilla.redhat.com/show_bug.cgi?id=1103452




Chris Murphy

Le 10/02/2015 02:01, Chris Murphy a ?crit :
> 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.
I'd like to be able to create either a simple RAID 1 layout with two 
disks, with a separate /boot partition, or a simple RAID 5 layout with 4 
disks, with a separate /boot partition too.

The layouts are described in this little Slackware-based HOWTO I wrote, 
and which I'm using on my servers. It's in French, but the command-line 
bits are universal :o)

http://www.microlinux.fr/slackware/Linux-HOWTOs/LAN-Server-HOWTO.txt

Cheers,

Niki

-- 
Microlinux - Solutions informatiques 100% Linux et logiciels libres
7, place de l'?glise - 30730 Montpezat
Web  : http://www.microlinux.fr
Mail : info at microlinux.fr
T?l. : 04 66 63 10 32