Re: [Hampshire] Software RAID1 install problems

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Author: Imran Chaudhry via Hampshire
To: Hampshire LUG Discussion List
CC: Imran Chaudhry
Subject: Re: [Hampshire] Software RAID1 install problems
Thanks James. Happily I sorted the problem out.

Turns out the installers of CentOS, Debian and Ubuntu will not
automatically create a BIOS GRUB partiton on the second disc when
software RAID is chosen. Only the first disc gets this partition.

This might be a edge-case bug, since it occurs when GPT and software
RAID is used. I'll report it to the respective upstream Bugzilla's.
The third screenshot in the album shows the error thrown by the CentOS
installer. This is what actually tipped me off because the graphical
installer displays a detailed partition summary and from checking that
I was able to see the missing "create BIOS GRUB partition" command for
the 2nd HDD.

What I did was to boot into a system rescue USB and use parted to
remove the partition table, create a new GPT one on each afresh and
then manually add a 1M BIOS GRUB partition to both discs. The commands
can be seen in the yellow terminal in the album below. This partition
is where GRUB installs some crucial 2nd stage boot-loader files when
using GPT partition tables. You need to use GPT to use discs >2T in

Anyway, I then proceeded with an Ubuntu Server 18.04 install. I chose
to manually create the partitions I needed and proceed with
configuring my software RAID array and then install went off without a
hitch. The fifth screenshot shows the final partition layout from the
Ubuntu installer.

As a side-note, prior to the above I was able to get a RAID1 system up
and running but without GRUB installed on one of the discs. My
question is: if the non-GRUB disc has the OS on it as normal, how can
I boot into it without GRUB?

On 19 May 2018 at 14:47, James Courtier-Dutton via Hampshire
<hampshire@???> wrote:
> On 19 May 2018 at 14:38, Imran Chaudhry via Hampshire
> <hampshire@???> wrote:
>> Hello All,
>> Having a spot of bother with something that should be straightfroward.
>> I'm setting up RAID1 Linux server install. The hardware is a HP
>> Microserver N54L. It has a non-UEFI BIOS.
>> I want to install a long-term support Linux server-oriented distro. So
>> far I've tried both CentOS 7 and Ubuntu 18.04 LTS.
>> I want to install the OS on two 4Tb discs as software RAID1 (mdadm)
> I normally leave space of about 100MB at the beginning of the disk for
> boot stuff (grub/bios boot), and then 1GB for the /boot partition.
> I don't know what the minimal you can get away with is, but 1GB from
> 4TB is minimal in my book.
> Then mirror the rest for RAID1.
> Kind Regards
> James
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