[CentOS] mdraid Q on c6...

Sun Jun 22 12:28:54 UTC 2014
Ljubomir Ljubojevic <centos at plnet.rs>

On 06/22/2014 10:15 AM, John R Pierce wrote:
> so, I installed a c6 system offsite today, had to do it in a hurry.
> box has 2 disks meant to be mirrored...  I couldn't figure out how to
> get anaconda to build a LVM root on a mirror, so I ended up just
> installing a /boot and vg_system on sda and raid it later.
> every howto I find for linux says to half-raid the OTHER disk, COPY
> everything to it, then boot from it and wipe the first disk and then
> bond it as a mirror of the 2nd.   Thats kind of ugly.
> in solaris, you can tell it that your existing partition is half of a
> mirror, update /etc/vfstab, then reboot, and then join a mirror to it.
> this seems much cleaner to me than copying everything.
> I tried to do this the solaris way, and at the first step, am told...
>      # mdadm --create /dev/md0 --level=mirror --raid-devices=2 /dev/sda2
>      missing
>      mdadm: cannot open /dev/sda2: Device or resource busy
> /dev/sda2 contains the LVM root vg...
> so... I'm thinking I''ll boot a rescue system from usb, create the half
> mirror, then reboot to the incomplete raid and add mirror /dev/sdb2
> will the VG be found on /dev/md0 instead of on /dev/sda2 ?
> if so, is there any other reason this won't work?

This is a best RAID tutorial I saw so far, and I made it better and 
safer (commands by just copying will fail due to /dev/sdx naming): 

Ljubomir Ljubojevic
(Love is in the Air)
PL Computers
Serbia, Europe

StarOS, Mikrotik and CentOS/RHEL/Linux consultant