Re:

[Michael Evans <mjevans1983@gmail.com>]

On Wed, Jan 6, 2010 at 6:19 AM, Lapohos Tibor <tibor.lapohos@rogers.com> wrote:
> Hello,
>
> I successfully set up an Intel Matrix Raid device with a RAID1 and a RAID0 volume, each having a couple of partitions, but then I could not install GRUB2 on the RAID1 volume, which I wanted to use to boot from and mount as root. It turned out that the "IMSM" metadata is not supported in GRUB2 (v1.97.1) just yet, so I had to turn away from my original plan.
>
> To "imitate" the setup I originally wanded, I turned both of my drives into AHCI controlled devices in the BIOS (instead of RAID), and I partitioned them to obtain /dev/sda[12] and /dev/sdb[12].
>
> Then I used /dev/sd[ab]1 to build a RAID1 set, and /dev/sd[ab]2 to create a RAID0 set using mdadm v 3.0.3:
>
>> mdadm -C /dev/md0 -v -e 0 -l 1 -n 2 /dev/sda1 /dev/sdb1
>> mdadm -C /dev/md1 -v -e 0 -l 0 -n 2 /dev/sda2 /dev/sdb2
>
> I set the metadata type to 0.90 because I would like to boot from it and allow the kernel to auto-detect the RAID devices while it's booting, in order to can get away from using an intitrd (I am building my own distribution based on CLFS x86_64 multilib).
>
> I used cfdisk to partition both of the /dev/md[01] devices, and I obtained /dev/md0p[123] and /dev/md1p[12]. The plan is to use /dev/md0p1 as a RAID1 root partition, and have the system boot from /dev/md0. I formatted /dev/md0p1 as
>
>> mk2efs -t ext4 -L OS /dev/md0p1
>
> To this point, things went smoothly. mdadm -D... and mdadm -E... did report back working devices as intended. Then mounted /dev/md0p1 on a directory called /root/os, and I did
>
>> grub-install --root-directory=/root/os /dev/md0
>
> or
>
>> grub-install --root-directory=/root/os "md0"
>
> and I got a warning and an error message: "Your embedding area is unusually small.  core.img won't fit in it." and "Embedding is not possible, but this is required when the root device is on a RAID array or LVM volume."
>
> What did I do wrong, and how do I fix it? Thanks ahead,
> Tibor
>
>
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Grub wants to embed (copy it's executable) in to the area between the
MBR style layout (sector 0 of a drive) and the first partition on that
drive (typically starts as early as sector 63).  Try starting the
first partition at something like a 1 or 2 mb offset from the start of
the drive.  That should likely be enough space.
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