There are a lot of HowTO’s on how to install a Raid using mdadm on Linux. Now I just created one device /dev/md0 and after a reboot it was gone, or rather renamed to /dev/md127 or /dev/md/HOSTNAME:0
Here is the creation of a Raid 6 with one spare disk, spanning 9 disks in total (yeah no one would waste so many disks, whatever):
sudo mdadm --create /dev/md0 --level=6 --raid-devices=8 --spare-devices=1 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 /dev/sdg1 /dev/sdh1 /dev/sdi1
The problem is that the config file seems to not like too many parameters. Most tutorials suggest to create the config like this (after creating the raid):
sudo mdadm --detail --scan --verbose > /etc/mdadm/mdadm.conf
With this, the config, at least on Ubuntu 12.10 with mdadm v.3.2.5 – 18th May 2012, is not able to mount the raid anymore. The only way I got it to work is to keep only one single line your config:
ARRAY /dev/md0 uuid=.....
With absolutely no options except the uuid! Weird, but it works now.