[arch-dev-public] Changing raid/raid-partitions initcpio hooks

Tobias Powalowski t.powa at gmx.de
Wed Feb 18 16:40:06 EST 2009

Hi guys,
while experimenting with different raid setups in kvm, i found out our raid 
support is not really ideal.

The status now:
- raid hook(inlcuded in mkinitcpio package) does assemble normal raid:
  but if a drive fails it will fail to boot after it.
  i'm not 100% sure if it can handle all types of raid levels, partitionable 
  mdp raid doesn't work at all with this hook for sure.
- raid-partitions(included in mdadm package) can only assemble 1 raid 
  partition array, which is imho bad you should be able to assemble more than 
  one raid partition device from commandline, if you wish to do so.
- UUID is not supported in any of both.

Shouldn't we replace all this with 1 hook which can handle all these cases?
Now comes the point, to achive this, mdadm will be needed in initramfs which 
means having a 900k static binary in early boot sequence. 
(raid-partitions hook already uses this binary)
The trick i thought of, would be to generate dynamically a mdadm.conf file 
from boot commandline, which will use the old syntax of assembling + adding a 
new syntax for UUID support.
Sample code is uploaded here:
(not yet tested to boot a system, it's sample code!)

Should this replace an existing hook or a be brand new hook?
What should happen to the other hooks, in order to not break a user setup.
Doing it with a NEWS Item and a installation message should be fine imho.

What do you guys think of this?
Thanks for your input.

Tobias Powalowski
Archlinux Developer & Package Maintainer (tpowa)
tpowa at archlinux.org
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