Re: LVM on software RAID - LILO
On Sat, Oct 23, 2004 at 07:00:47PM +0300, Fabian Fagerholm wrote:
> On Sat, 2004-10-09 at 21:16 +0300, Fabian Fagerholm wrote:
> > I tried the following (3 x HDD):
> >
> > In partman, set up the three disks to have identical partition tables:
> >
> > * A small primary partition with boot flag set.
> > * A large logical partition.
> > * A small logical partition.
> >
> > I then took all the small primary partitions and created a RAID1 out of
> > them (/dev/md/0). I put /boot on this (ReiserFS).
> >
> > Then, I took the large logical partitions and created a RAID5 out of
> > them (/dev/md/1). The small logical partitions were marked as swap.
> >
> > I manually ran pvcreate and vgcreate on /dev/md/1. Then, using partman,
> > I added logical volumes for /, /usr, /var, /home and /tmp. Still using
> > partman, I assigned the mount points and chose to format all logical
> > volumes as ReiserFS. Partman finished its work.
> >
> > However, as a result of this, GRUB install was disabled, and LILO was to
> > be used instead. LILO install didn't work; I tried specifying the first
> > disk's MBR manually but LILO failed whatever I tried.
> >
> > Am I right in assuming that both LILO and GRUB should work, since they
> > can read the kernel image and initrd from one of the disks in the RAID1
> > array that comprises /boot, and the initrd contains all neccessary
> > things to access / on RAID5 and LVM? Ie. is it enough that /boot is on
> > RAID1 or plain partition with no LVM?
>
> I just tried with a cd image downloaded from the following url:
> http://cdimage.debian.org/pub/cdimage-testing/daily/i386/current/sarge-i386-netinst.iso
> The build date was 22-Oct-2004.
>
> It's now possible to mark a RAID array for use with LVM. However, if I
> do the above, the installer disables GRUB, and LILO refuses to install
> to the default option ("/dev/md1: Master Boot record") which seems to be
> wrong for this kind of setup. I expected to see /dev/md0 as the default.
>
> I tried installing on /dev/md0
> and /dev/ide/host0/bus0/target0/lun0/disc, but I just got the error
> messages "The path /dev/md0 does not represent a partition of a hard
> disk device" and "Running /sbin/lilo failed with error code "1"".
>
> However, it does seem that it's impossible to do what I wanted. When I
> adjusted the scenario, I got everything to work. I split up the three
> disks into three partitions:
>
> * A primary partition with the boot flag set,
> * a large logical partition and
> * a small logical partition.
>
> I then marked the primary partitions for RAID use, the large logical
> partition for RAID use, and the small logical partition as swap.
>
> Then, I assembled a RAID1 with the three primary partitions, and a RAID5
> with the three large logical partitions. After that (and here's the key
> difference), I chose to format the RAID1 as ReiserFS and mount it as /,
> and created an LVM volume group on the RAID5, which I populated with
> logical volumes for /usr, /var, /home and /tmp. All partitions were
> ReiserFS.
>
> This worked like a charm, and GRUB was nicely installed.
>
> So: it should be clearly documented that it is not possible, in any way,
> to put your / on RAID5, not with GRUB and not with LILO. My assumption
> that it would be enough for the boot loader to access the initrd from
> one of the disks in the RAID1 array (with /boot on it) to be able to
> access / on RAID5 was apparently not correct -- or at least it doesn't
> work in d-i when installing the boot loader. Perhaps it would work if
> booting off another medium and skipping the installation of a boot
> loader in d-i.
I think you struct the same lilo-installer bug that I did yesterday, when I
was doing some RAID1 experiments. I told it to use /dev/discs/disc0/disc and
it installed fine, iirc. Joey said it's a known bug.
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