Re: RAID1 on / planned?

[Finn-Arne Johansen <faj@bzz.no>]

On Mon, Jun 14, 2004 at 09:51:51PM +1000, Andrew Pollock wrote:
> On Sun, Jun 13, 2004 at 02:49:26PM +0100, Martin Michlmayr wrote:
> > * Charles Steinkuehler <charles@steinkuehler.net> [2004-06-11 14:45]:
> > > I'm pretty handy with shell scripting, and could probably come up with a 
> > > fix to the grub stuff (espeically with the nice auto-detect stuff in 
> > > mkinitrd already working!), if that would be of assistance.
> > 
> > It would be good if you could find out why LILO and GRUB fail in the
> > first place instead of being able to cope with the situation.  Then we
> > can figure out whether we need to put in a workaround or whether
> > LILO/GRUB should just get fixed.
> 
> I'll look into it more closely after exams (if it isn't sorted by then) but
> I think in the case of GRUB (from what I've read wrt the hacks to get it to
> work) it's because /dev/md/0 doesn't correspond to a BIOS device.
> 
> I get the general impression that GRUB, whilst a very cool bootloader, is a
> bit rough around the edges when you want to do some of the more esoteric
> stuff...

I dont know if this applies to other architecures than i386, but here is what I done to successfully install on SWRaid: 

Boot in expert mode

Load the following components: 
  autopartkit
  eject-udeb
  lvmcfg
  mdcfg

create partitions: 
  some small for / ( I choose 256-512 MB ) 
  this is the first partion on two disks
  use the rest of the two disks as lvm, on logical partitions
  all 4 partitions should be set up to be used as raid devices

  Then continue to set up the partitions as softwareraid
  the two smaller primary partions as one raid set, 
  and the two larger as another. 

  Then to set up LVM, I need to switch to a terminal (Alt+F2)
  and do 
   pvcreate /dev/md/1
   vgcreate vg_raid /dev/md/1

  Then I switch back and creates three logical volumes
   lv_usr, lv_var, and lv_swap
  And format and mount the partitions

Install the Basesystem
  but before the installation of the kernel, switch to a terminal again
  (Alt+F2), and do a:
    chroot /target apt-get install mdadm

  Then switch back and install the kernel

Installation of grub: 
  The "grub-install", and "update-grub" both have problems with swraid
  root partition.
  The workaround is simple (again in a terminal):
    chroot /target 
     apt-get install grub
     mkdir /boot/grub/
     cp /usr/lib/grub/i386_pc/stage[12] /boot/grub
     cp /usr/lib/grub/i386_pc/*stage1_5 /boot/grub
     grub --no-floppy
      root (hd0,0)
      setup (hd0)
      quit
     exit

then "continue without bootloader"
and finnish the installation and reboot

When the installation reboots, you enter
 root (hd0,0)
 kernel /vmlinuz root=/dev/md0 ro
 initrd /initrd.img
 boot

Then you may continue with the second stage installer

What's missing for this to be easy: 
It would be nice if we could set up lvm on top of raid1 without the
need for switching to the console, and creating the physical volume,
and the volume group manually.
It would be nice if mdadm was installed before the kernel was to be
installed. 

The last caveat is the setup of grub. I'll try to look at that one. 

-- 
Finn-Arne Johansen 
faj@bzz.no
http://bzz.no/