Re: Grub2 and and mdraid

[Simon Hobson]

Patrick Begou <address@hidden> wrote:

> for a while now I'm trying to set up grub to boot on a md array without any 
> success. The system is actualy runing with: 
> /dev/sda2 mounted on /boot 
> /dev/sda3 a physical volume and /dev/mapper/pve-root mounted on /root 
> (proxmox distribution) 
> 
> I've added a second disk /dev/sdc to move to a RAID1 config. 
> 
> /dev/sdc2 is part of a degraded raid1 array /dev/md2  and /dev/md2 is an ext4 
> filesystem for /boot 



> But every time I get in the a rescue shell, saying the disk is not found. In 
> the "ls" command of the rescue shell no md devices seams available. 

What happens if you try to use /dev/sdc2 as the boot volume instead of /dev/md2 
?

I don't confess any great knowledge, but I have a number of systems (Debian 
Wheezy) which "just work" booting from RAID1 arrays. I believe that even 
without raid support, grub can use any member of the array as they are all 
identical copies (only applies to RAID1) - and as long as they are only used 
read-only (as Grub does while booting) then it won't damage the array.
Once the kernel and initrd are loaded, then that will contain all the proper 
raid support anyway.

TBH I don't know if mine are using the raid array or a single member of it - 
grub.cfg is using --fs-uuid to reference the volume anyway, so while I see 
"insmod mdraid" in my config, I have no idea whether it's using raid or not.