:: [DNG] beowulf and partitionable md …
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Author: Adrian Zaugg
To: dng
Subject: [DNG] beowulf and partitionable md raids

Dear Dev1ers

Unfortunately Debian still thinks partionable RAIDs are not worth to
integrate into the installer. Like this it is still hard work to get a
Devuan beowulf on a bootable partionable md raid1 and with UEFI not even
possible according to my tries...

First of all I believe partitionable md raids are superior to "usual"
mds which just span over partitions on different disks instead over the
whole disk. If a disks dies and has to be replaced for the usual mds one
needs to copy the partition table first using sfdisk -d /dev/workingdisk
| sfdisk /dev/newdisk and install the boot loader on it, where as with

partionable mds you can just hot add a new disk to the running raid
using mdadm. Maybe that changed until today without me being aware of.

I was able to set up a ascii on a partitionable raid0 including /boot
using BIOS and DOS disk labels (with metadata 1.2). I failed miserably
doing this using a GPT partition scheme and UEFI. Did someone manage to
achieve this?

Recently I retried using the beowulf installer, changed to the console
to setup and format the md. The installer did not recognise the
partitions are formatted and suggest refomatting them. Since I don't
know if it pays attention to the stride-size and stripe-width options of
Ext4 I don't want to let it do it. I then found out that it will install
on it, when the raid is mounted in /target (you also need to bind mount
/dev, /dev/pts, mount /sys and /proc as well). This definitively used to
be different in earlier versions of the installer. Would it be hard to
enhance the installer to fully support partitionable mds?

Regards, Adrian.